docs: add rustdoc comments to all module options

This part of an upcoming effort to generate documentation from code.

Pushing this out before that stage so that the JSON schema is fully documented.

src/modules/custom/button.rs

@@ -11,13 +11,43 @@ use super::{CustomWidget, CustomWidgetContext, ExecEvent, WidgetConfig};
 
 #[derive(Debug, Deserialize, Clone)]
 pub struct ButtonWidget {
+    /// Widget name.
+    ///
+    /// **Default**: `null`
     name: Option<String>,
+
+    /// Widget class name.
+    ///
+    /// **Default**: `null`
     class: Option<String>,
+
+    /// Widget text label. Pango markup and embedded scripts are supported.
+    ///
+    /// This is a shorthand for adding a label widget to the button.
+    /// Ignored if `widgets` is set.
+    ///
+    /// This is a [Dynamic String](dynamic-values#dynamic-string).
+    ///
+    /// **Default**: `null`
     label: Option<String>,
+
+    /// Command to execute. More on this [below](#commands).
+    ///
+    /// **Default**: `null`
     on_click: Option<String>,
-    widgets: Option<Vec<WidgetConfig>>,
+
+    /// Orientation of the button.
+    ///
+    /// **Valid options**: `horizontal`, `vertical`, `h`, `v`
+    /// <br />
+    /// **Default**: `horizontal`
     #[serde(default)]
     orientation: ModuleOrientation,
+
+    /// Modules and widgets to add to this box.
+    ///
+    /// **Default**: `null`
+    widgets: Option<Vec<WidgetConfig>>,
 }
 
 impl CustomWidget for ButtonWidget {