Kirin UI
Embedded common code used across several Mine Little Pony projects to create their GUIs.
If you're a player
This mod is a library and is usually embedded or installed as a dependency for other mods, so installing it on its own doesn't do anything.
It will occasionally get updates independent of other projects that depend on it, so whilst installing it separately is not recommended it is permitted if you're having issues that updating solves but the downstream project hasn't (or can't) be updated for whatever reason.
If you're a mod developer
Kirin provides support for creating GUIs, and hooking into existing GUIs to add a variety of different controls: Buttons, Toggles, Cyclers, and scrolling containers that makes them both simpler and easier to configure, with more customisation options than the regular game's classes. It also provides an advanced configuration system for loading a config file in json format with support for live updates whilst the game is running.
For more on how to use it, I recommend checking out the projects source on github.