feat: add override based on filetype in addition to buftype

## Details

Similar to `overrides.buftype` added `overrides.filetype` which allows
the same sets of configurations to be overridden for specific file
types.

For instance to disable signs in gitcommit files:

```lua
require('render-markdown').setup({
    file_types = { 'markdown', 'gitcommit' },
    overrides = {
        filetype = {
            gitcommit = { sign = { enabled = false } },
        },
    },
})
```

Author: MeanderingProgrammer

README.md

@@ -514,10 +514,10 @@ require('render-markdown').setup({
     overrides = {
         -- Overrides for different buftypes, see :h 'buftype'
         buftype = {
-            nofile = {
-                sign = { enabled = false },
-            },
+            nofile = { sign = { enabled = false } },
         },
+        -- Overrides for different filetypes, see :h 'filetype'
+        filetype = {},
     },
     -- Mapping from treesitter language to user defined handlers
     -- See 'Custom Handlers' document for more info

doc/render-markdown.txt

@@ -544,10 +544,10 @@ Full Default Configuration ~
         overrides = {
             -- Overrides for different buftypes, see :h 'buftype'
             buftype = {
-                nofile = {
-                    sign = { enabled = false },
-                },
+                nofile = { sign = { enabled = false } },
             },
+            -- Overrides for different filetypes, see :h 'filetype'
+            filetype = {},
         },
         -- Mapping from treesitter language to user defined handlers
         -- See 'Custom Handlers' document for more info

lua/render-markdown/health.lua

@@ -5,7 +5,7 @@ local M = {}
 
 ---@private
 ---@type string
-M.version = '6.1.10'
+M.version = '6.1.11'
 
 function M.check()
     vim.health.start('render-markdown.nvim [version]')

lua/render-markdown/init.lua

@@ -139,6 +139,7 @@ local M = {}
 
 ---@class (exact) render.md.UserConfigOverrides
 ---@field public buftype? table<string, render.md.UserBufferConfig>
+---@field public filetype? table<string, render.md.UserBufferConfig>
 
 ---@class (exact) render.md.UserBufferConfig
 ---@field public enabled? boolean
@@ -548,10 +549,10 @@ M.default_config = {
     overrides = {
         -- Overrides for different buftypes, see :h 'buftype'
         buftype = {
-            nofile = {
-                sign = { enabled = false },
-            },
+            nofile = { sign = { enabled = false } },
         },
+        -- Overrides for different filetypes, see :h 'filetype'
+        filetype = {},
     },
     -- Mapping from treesitter language to user defined handlers
     -- See 'Custom Handlers' document for more info

lua/render-markdown/state.lua

@@ -69,9 +69,11 @@ M.get_config = function(buf)
     local config = configs[buf]
     if config == nil then
         config = M.default_buffer_config()
-        local buftype_config = M.config.overrides.buftype[util.get_buf(buf, 'buftype')]
-        if buftype_config ~= nil then
-            config = vim.tbl_deep_extend('force', config, buftype_config)
+        for _, name in ipairs({ 'buftype', 'filetype' }) do
+            local override_config = M.config.overrides[name][util.get_buf(buf, name)]
+            if override_config ~= nil then
+                config = vim.tbl_deep_extend('force', config, override_config)
+            end
         end
         configs[buf] = config
     end
@@ -426,28 +428,31 @@ function M.validate()
     local overrides = config.overrides
     append_errors('render-markdown.overrides', overrides, {
         buftype = { overrides.buftype, 'table' },
+        filetype = { overrides.filetype, 'table' },
     })
-    for name, override in pairs(overrides.buftype) do
-        local path = 'render-markdown.overrides.buftype.' .. name
-        append_errors(path, override, {
-            enabled = { override.enabled, 'boolean', true },
-            max_file_size = { override.max_file_size, 'number', true },
-            debounce = { override.debounce, 'number', true },
-            render_modes = string_array(override.render_modes, true),
-            anti_conceal = { override.anti_conceal, 'table', true },
-            heading = { override.heading, 'table', true },
-            code = { override.code, 'table', true },
-            dash = { override.dash, 'table', true },
-            bullet = { override.bullet, 'table', true },
-            checkbox = { override.checkbox, 'table', true },
-            quote = { override.quote, 'table', true },
-            pipe_table = { override.pipe_table, 'table', true },
-            callout = { override.callout, 'table', true },
-            link = { override.link, 'table', true },
-            sign = { override.sign, 'table', true },
-            win_options = { override.win_options, 'table', true },
-        })
-        validate_buffer_config(path, override, true)
+    for name, value_override in pairs(overrides) do
+        for value, override in pairs(value_override) do
+            local path = string.format('render-markdown.overrides.%s.%s', name, value)
+            append_errors(path, override, {
+                enabled = { override.enabled, 'boolean', true },
+                max_file_size = { override.max_file_size, 'number', true },
+                debounce = { override.debounce, 'number', true },
+                render_modes = string_array(override.render_modes, true),
+                anti_conceal = { override.anti_conceal, 'table', true },
+                heading = { override.heading, 'table', true },
+                code = { override.code, 'table', true },
+                dash = { override.dash, 'table', true },
+                bullet = { override.bullet, 'table', true },
+                checkbox = { override.checkbox, 'table', true },
+                quote = { override.quote, 'table', true },
+                pipe_table = { override.pipe_table, 'table', true },
+                callout = { override.callout, 'table', true },
+                link = { override.link, 'table', true },
+                sign = { override.sign, 'table', true },
+                win_options = { override.win_options, 'table', true },
+            })
+            validate_buffer_config(path, override, true)
+        end
     end
 
     for name, handler in pairs(config.custom_handlers) do

lua/render-markdown/types.lua

@@ -114,6 +114,7 @@
 
 ---@class (exact) render.md.ConfigOverrides
 ---@field public buftype table<string, render.md.UserBufferConfig>
+---@field public filetype table<string, render.md.UserBufferConfig>
 
 ---@class (exact) render.md.BufferConfig
 ---@field public enabled boolean