Trackpad Gesture Support

Somewhat of a weird suggestion maybe, but would you be open to expand this tool's functionality to monitor specific trackpad gestures? (e.g. four finger taps, various swipes, "tip-taps") This tool has largely replaced the paid app bettertouchtool for me, except that it lacks binding trackpad gestures to commands. And because running both seems wasteful, I prefer skhd's way of configuration and skdh seems less recourse intensive, I would really like to use it for trackpad monitoring as well. Trackpad gesutres can be monitored through some sort of [private API](https://gist.github.com/rmhsilva/61cc45587ed34707da34818a76476e11). I would be interested in implementing this functionality myself.

As not really everyone will need this probably, it seems more resource friendly to have a switch to enable trackpad gestures.

Start by reviewing the linked private API and skhd's current configuration and daemon behavior. Define the supported gestures, the opt-in switch, command-binding semantics, and resource expectations; done means enabled gestures trigger configured commands without requiring BetterTouchTool.

Written by the indexing model from the issue text.