Editor support Documentation (#3132)

depends on #3129 

cc @josh11b for review

utils/README.md

@@ -8,3 +8,18 @@ SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
 This directory collects tools and utilities that may be useful to both Carbon
 developers and developers writing Carbon code.
+
+## Editor Support
+
+-   [VSCode](./vscode/README.md)
+-   [Neovim](./nvim/README.md)
+-   [Vim](./vim/README.md)
+-   [IntelliJ](./textmate/README.md#intellij)
+-   [Atom](./textmate/README.md#atom)
+
+### Other Editors
+
+Any editor that supports Language server protocol and/or tree-sitter is
+supported. The editor just needs to be configured manually.
+`bazel build language_server` produces the language server binary.
+`utils/treesitter` contains the treesitter grammar.

utils/textmate/README.md

@@ -16,14 +16,20 @@ Clone the repository with Git and symlink/copy the `utils/textmate` directory to
 any of the paths TextMate will search through (you can find these paths in the
 TextMate documentation above).
 
+## IntelliJ
+
 If you are using IntelliJ or a IntelliJ Platform product, you can find
 documentation on
 [how to install TextMate bundles in IntelliJ](https://www.jetbrains.com/help/idea/textmate.html#import-textmate-bundles).
 Clone the repository with Git and open the `utils/textmate` directory inside the
 IntelliJ TextMate Bundle window.
 
+## Atom
+
 If you are using Atom, you can convert the bundle to an Atom-compatible one. See
 [the Atom documentation on how to do that.](https://flight-manual.atom.io/hacking-atom/sections/converting-from-textmate/)
 
+## Other
+
 For other editors that support TextMate bundles you can consult your editors
 documentation to see how to use the bundle.