ruby: Add support for "rubocop" language server (#14661)

Hi, this pull request adds support for `rubocop` language server. I
noticed that `ruby-lsp` LS is becoming more popular but it still lacks
diagnostics support in Zed. To cover that missing feature, it could be
good to use `rubocop` LS to show diagnostics alongside with the running
Ruby LSP.

Release Notes:

- N/A

---------

Co-authored-by: Marshall Bowers <elliott.codes@gmail.com>

docs/src/languages/ruby.md

@@ -16,7 +16,20 @@ To switch to `ruby-lsp`, add the following to your `settings.json`:
 {
   "languages": {
     "Ruby": {
-      "language_servers": ["ruby-lsp", "!solargraph", "..."]
+      "language_servers": ["ruby-lsp", "!solargraph", "!rubocop", "..."]
+    }
+  }
+}
+```
+
+The Ruby extension also provides support for `rubocop` language server for offense detection and autocorrection. To enable it, add the following to your
+`settings.json`:
+
+```json
+{
+  "languages": {
+    "Ruby": {
+      "language_servers": ["rubocop", "ruby-lsp", "!solargraph", "..."]
     }
   }
 }
@@ -83,6 +96,30 @@ Ruby LSP uses pull-based diagnostics which Zed doesn't support yet. We can tell
 }
 ```
 
+## Setting up `rubocop` LSP
+
+Zed currently doesn't install `rubocop` automatically. To use `rubocop`, you need to install the gem. Zed just looks for an executable called `rubocop` on your `PATH`.
+
+You can install the gem manually with the following command:
+
+```shell
+gem install rubocop
+```
+
+Rubocop has unsafe autocorrection disabled by default. We can tell Zed to enable it by adding the following to your `settings.json`:
+
+```json
+{
+  "lsp": {
+    "rubocop": {
+      "initialization_options": {
+        "safeAutocorrect": false
+      }
+    }
+  }
+}
+```
+
 ## Using the Tailwind CSS Language Server with Ruby
 
 It's possible to use the [Tailwind CSS Language Server](https://github.com/tailwindlabs/tailwindcss-intellisense/tree/HEAD/packages/tailwindcss-language-server#readme) in Ruby and ERB files.