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/slider.rs

@@ -17,18 +17,67 @@ use super::{CustomWidget, CustomWidgetContext, ExecEvent};
 
 #[derive(Debug, Deserialize, Clone)]
 pub struct SliderWidget {
+    /// Widget name.
+    ///
+    /// **Default**: `null`
     name: Option<String>,
+
+    /// Widget class name.
+    ///
+    /// **Default**: `null`
     class: Option<String>,
+
+    /// Orientation of the slider.
+    ///
+    /// **Valid options**: `horizontal`, `vertical`, `h`, `v`
+    /// <br />
+    /// **Default**: `horizontal`
     #[serde(default)]
     orientation: ModuleOrientation,
+
+    /// Script to run to get the slider value.
+    /// Output must be a valid number.
+    ///
+    /// **Default**: `null`
     value: Option<ScriptInput>,
+
+    /// Command to execute when the slider changes.
+    /// More on this [below](#slider).
+    ///
+    /// Note that this will provide the floating point value as an argument.
+    /// If your input program requires an integer, you will need to round it.
+    ///
+    /// **Default**: `null`
     on_change: Option<String>,
+
+    /// Minimum slider value.
+    ///
+    /// **Default**: `0`
     #[serde(default = "default_min")]
     min: f64,
+
+    /// Maximum slider value.
+    ///
+    /// **Default**: `100`
     #[serde(default = "default_max")]
     max: f64,
+
+    /// If the increment to change when scrolling with the mousewheel.
+    /// If left blank, GTK will use the default value,
+    /// determined by the current environment.
+    ///
+    /// **Default**: `null`
     step: Option<f64>,
+
+    /// The slider length.
+    /// GTK will automatically determine the size if left blank.
+    ///
+    /// **Default**: `null`
     length: Option<i32>,
+
+    /// Whether to show the value label above the slider.
+    ///
+    /// **Default**: `true`
     #[serde(default = "crate::config::default_true")]
     show_label: bool,
 }