docs: Document how to use project-specific settings for Ruby LSP (#27310)

I think it's helpful to illustrate how some settings can be added to the
project settings file rather than being global.

Release Notes:

- N/A

---------

Co-authored-by: Peter Tripp <peter@zed.dev>

docs/src/languages/ruby.md

@@ -158,6 +158,21 @@ Ruby LSP uses pull-based diagnostics which Zed doesn't support yet. We can tell
 }
 ```
 
+LSP `settings` and `initialization_options` can also be project-specific. For example to use [standardrb/standard](https://github.com/standardrb/standard) as a formatter and linter for a particular project, add this to a `.zed/settings.json` inside your project repo:
+
+```json
+{
+  "lsp": {
+    "ruby-lsp": {
+      "initialization_options": {
+        "formatter": "standard",
+        "linters": ["standard"]
+      }
+    }
+  }
+}
+```
+
 By default, Ruby LSP does not use `bundle exec` to run in the context of the bundle. To enable that, you can use the `use_bundler` configuration option:
 
 ```json