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/language/src/language_settings.rs

@@ -79,36 +79,90 @@ pub struct AllLanguageSettingsContent {
 
 #[derive(Clone, Default, Serialize, Deserialize, JsonSchema)]
 pub struct LanguageSettingsContent {
+    /// How many columns a tab should occupy.
+    ///
+    /// Default: 4
     #[serde(default)]
     pub tab_size: Option<NonZeroU32>,
+    /// Whether to indent lines using tab characters, as opposed to multiple
+    /// spaces.
+    ///
+    /// Default: false
     #[serde(default)]
     pub hard_tabs: Option<bool>,
+    /// How to soft-wrap long lines of text.
+    ///
+    /// Default: none
     #[serde(default)]
     pub soft_wrap: Option<SoftWrap>,
+    /// The column at which to soft-wrap lines, for buffers where soft-wrap
+    /// is enabled.
+    ///
+    /// Default: 80
     #[serde(default)]
     pub preferred_line_length: Option<u32>,
+    /// Whether to show wrap guides in the editor. Setting this to true will
+    /// show a guide at the 'preferred_line_length' value if softwrap is set to
+    /// 'preferred_line_length', and will show any additional guides as specified
+    /// by the 'wrap_guides' setting.
+    ///
+    /// Default: true
     #[serde(default)]
     pub show_wrap_guides: Option<bool>,
+    /// Character counts at which to show wrap guides in the editor.
+    ///
+    /// Default: []
     #[serde(default)]
     pub wrap_guides: Option<Vec<usize>>,
+    /// Whether or not to perform a buffer format before saving.
+    ///
+    /// Default: on
     #[serde(default)]
     pub format_on_save: Option<FormatOnSave>,
+    /// Whether or not to remove any trailing whitespace from lines of a buffer
+    /// before saving it.
+    ///
+    /// Default: true
     #[serde(default)]
     pub remove_trailing_whitespace_on_save: Option<bool>,
+    /// Whether or not to ensure there's a single newline at the end of a buffer
+    /// when saving it.
+    ///
+    /// Default: true
     #[serde(default)]
     pub ensure_final_newline_on_save: Option<bool>,
+    /// How to perform a buffer format.
+    ///
+    /// Default: auto
     #[serde(default)]
     pub formatter: Option<Formatter>,
+    /// Zed's Prettier integration settings.
+    /// If Prettier is enabled, Zed will use this its Prettier instance for any applicable file, if
+    /// project has no other Prettier installed.
+    ///
+    /// Default: {}
     #[serde(default)]
     pub prettier: Option<HashMap<String, serde_json::Value>>,
+    /// Whether to use language servers to provide code intelligence.
+    ///
+    /// Default: true
     #[serde(default)]
     pub enable_language_server: Option<bool>,
+    /// Controls whether copilot provides suggestion immediately (true)
+    /// or waits for a `copilot::Toggle` (false).
+    ///
+    /// Default: true
     #[serde(default)]
     pub show_copilot_suggestions: Option<bool>,
+    /// Whether to show tabs and spaces in the editor.
     #[serde(default)]
     pub show_whitespaces: Option<ShowWhitespaceSetting>,
+    /// Whether to start a new line with a comment when a previous line is a comment as well.
+    ///
+    /// Default: true
     #[serde(default)]
     pub extend_comment_on_newline: Option<bool>,
+    /// Inlay hint related settings.
     #[serde(default)]
     pub inlay_hints: Option<InlayHintSettings>,
 }
@@ -128,8 +182,11 @@ pub struct FeaturesContent {
 #[derive(Copy, Clone, Debug, Serialize, Deserialize, PartialEq, Eq, JsonSchema)]
 #[serde(rename_all = "snake_case")]
 pub enum SoftWrap {
+    /// Do not soft wrap.
     None,
+    /// Soft wrap lines that overflow the editor
     EditorWidth,
+    /// Soft wrap lines at the preferred line length
     PreferredLineLength,
 }
 
@@ -148,18 +205,26 @@ pub enum FormatOnSave {
 #[derive(Copy, Clone, Debug, Serialize, Deserialize, PartialEq, Eq, JsonSchema)]
 #[serde(rename_all = "snake_case")]
 pub enum ShowWhitespaceSetting {
+    /// Draw tabs and spaces only for the selected text.
     Selection,
+    /// Do not draw any tabs or spaces
     None,
+    /// Draw all invisible symbols
     All,
 }
 
 #[derive(Clone, Debug, Default, Serialize, Deserialize, PartialEq, Eq, JsonSchema)]
 #[serde(rename_all = "snake_case")]
 pub enum Formatter {
+    /// Format files using Zed's Prettier integration (if applicable),
+    /// or falling back to formatting via language server.
     #[default]
     Auto,
+    /// Format code using the current language server.
     LanguageServer,
+    /// Format code using Zed's Prettier integration.
     Prettier,
+    /// Format code using an external command.
     External {
         command: Arc<str>,
         arguments: Arc<[String]>,
@@ -168,6 +233,9 @@ pub enum Formatter {
 
 #[derive(Copy, Clone, Debug, Serialize, Deserialize, JsonSchema, PartialEq, Eq)]
 pub struct InlayHintSettings {
+    /// Global switch to toggle hints on and off.
+    ///
+    /// Default: false
     #[serde(default)]
     pub enabled: bool,
     #[serde(default = "default_true")]