Document widgets in music and nvidia_gpu blocks (#2142)

Fixes #1962

Author: bim9262

src/blocks/music.rs

@@ -46,11 +46,17 @@
 //! `volume_icon` | Icon based on volume. Missing if unsupported.    | Icon
 //! `volume`      | Current volume. Missing if muted or unsupported. | Number
 //!
+//! Widget           | Placeholder
+//! -----------------|-------------
+//! `play_pause_btn` | `$play`
+//! `next_btn`       | `$next`
+//! `prev_btn`       | `$prev`
+//!
 //! Action          | Default button
 //! ----------------|------------------
-//! `play_pause`    | Left on `$play`
-//! `next`          | Left on `$next`
-//! `prev`          | Left on `$prev`
+//! `play_pause`    | Left on `play_pause_btn`
+//! `next`          | Left on `next_btn`
+//! `prev`          | Left on `prev_btn`
 //! `next_player`   | Right
 //! `seek_forward`  | Wheel Up
 //! `seek_backward` | Wheel Down

src/blocks/nvidia_gpu.rs

@@ -33,12 +33,17 @@
 //! `clocks`      | Number | Hertz
 //! `power`       | Number | Watts
 //!
+//! Widget    | Placeholder
+//! ----------|-------------
+//! `mem_btn` | `$memory`
+//! `fan_btn` | `$fan_speed`
+//!
 //! Action                  | Default button
 //! ------------------------|----------------
-//! `toggle_mem_total`      | Left on `$memory`
-//! `toggle_fan_controlled` | Left on `$fan_speed`
-//! `fan_speed_up`          | Wheel Up on `$fan_speed`
-//! `fan_speed_down`        | Wheel Down on `$fan_speed`
+//! `toggle_mem_total`      | Left on `mem_btn`
+//! `toggle_fan_controlled` | Left on `fan_btn`
+//! `fan_speed_up`          | Wheel Up on `fan_btn`
+//! `fan_speed_down`        | Wheel Down on `fan_btn`
 //!
 //! # Example
 //!