Display setting documentation in settings.json (#3936)

Let this screenshot of settings.json speak for itself: 

![image](https://github.com/zed-industries/zed/assets/24362066/fca60383-1788-43f9-803b-00f083394c8a)

Release Notes:
- Added code completion & on-hover documentation to Zed's settings.json
file.

---------

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

crates/client/src/client.rs

@@ -352,9 +352,16 @@ pub struct TelemetrySettings {
     pub metrics: bool,
 }
 
+/// Control what info is collected by Zed.
 #[derive(Default, Clone, Serialize, Deserialize, JsonSchema)]
 pub struct TelemetrySettingsContent {
+    /// Send debug info like crash reports.
+    ///
+    /// Default: true
     pub diagnostics: Option<bool>,
+    /// Send anonymized usage data like what languages you're using Zed with.
+    ///
+    /// Default: true
     pub metrics: Option<bool>,
 }