Update README with available functions

README.md

@@ -15,6 +15,17 @@ You can use tiny scripts written in [Expr][expr] to automatically perform action
 
 The reason I wrote this tool is to be able to toggle playback in Spotify when I mute/unmute a certain channel on a mixer. The scripts in [examples](./examples) show how to use it. Make sure to replace the `MIXER_ID` and set the right value for `fader`.
 
+## Functions
+
+These are the functions you can call from your scripts:
+
+| Function   | Arguments   | Example                | Purpose   |
+| :--------- | :---------- | :--------------------- | :-------- |
+| PlayPause[^1]  | player name | `PlayPause("spotify")` | Toggle music play/pause |
+| RunCommand | command     | `RunCommand("notify-send", "title", "body")` | Execute arbitrary command |
+
+[^1]: `PlayPause` uses the D-Bus user session and as such only works on Linux
+
 ## Running
 
 A systemd unit file is included. You can install this in `$HOME/.config/systemd/user` or `/lib/systemd/user`. After a `daemon-reload` you can start it with `systemctl --user start gopherxlr.service`.