[skip changelog] Fix issues with command reference section of the documentation's navigation pane (#801)

* Correct arduino-cli command name in command reference navigation

When no title is defined, the documentation system automatically generates a title from the filename. This resulted in the command being incorrectly called "Arduino cli" in the command reference section of the documentation's navigation pane.

* Add burn-bootloader to the command reference navigation

It's required to add an entry to mkdocs.yml before the command will be shown in the command reference section of the documentation's navigation pane.

Author: per1234

mkdocs.yml

@@ -60,12 +60,13 @@ nav:
   - CONTRIBUTING.md
   - FAQ.md
   - Command reference:
-    - commands/arduino-cli.md
+    - arduino-cli: commands/arduino-cli.md
     - board: commands/arduino-cli_board.md
     - board attach: commands/arduino-cli_board_attach.md
     - board details: commands/arduino-cli_board_details.md
     - board list: commands/arduino-cli_board_list.md
     - board listall: commands/arduino-cli_board_listall.md
+    - burn-bootloader: commands/arduino-cli_burn-bootloader.md
     - cache: commands/arduino-cli_cache.md
     - cache clean: commands/arduino-cli_cache_clean.md
     - compile: commands/arduino-cli_compile.md