Add documentation for lsp4mp

I didn't set a demo image,
since end users are expected to use use vscode-microprofile or
intellij-quarkus to use lsp4mp.

Signed-off-by: David Thompson <davthomp@redhat.com>

Author: datho7561

docs/languages/lsp4mp.md

@@ -4,4 +4,12 @@ sidebar_position: 7
 
 # LSP4MP
 
-[Visit the GitHub](https://github.com/eclipse/lsp4mp)
+lsp4mp is a [language server](https://microsoft.github.io/language-server-protocol/) that provides IDE features for working with projects that use [MicroProfile](https://microprofile.io/).
+
+It powers [VS Code Tools for MicroProfile](/docs/languages/vscode-microprofile) and
+[Intellij Quarkus](/docs/languages/intellij-quarkus),
+as well as [Liberty Tools for Intellij](https://github.com/OpenLiberty/liberty-tools-intellij).
+
+It provides IDE features for `microprofile-config.properties` files and enhances the existing Java IDE support with MicroProfile-specific features.
+
+[Visit the GitHub](https://github.com/eclipse/lsp4mp)