LibLCU.ts communicates with the League Client server, pretending to be the UX part of the client.
It's implemented in TypeScript and isn't close to completion at the moment.

Some things do work, and there is a lot to learn, but currently it's not instantly usable like a regular NPM library.
For now, if you really want to use it, take a look at the Client class and explore from there.

While this project is mostly made for fun, it has some practical use too.
The original client UI / UX (LeagueClientUx) utilizes Chromium Embedded Framework, running a large Chromium instance for just the UI. This takes up system resources, while the server (LeagueClient) is actually rather efficient.
LibLCU.ts aims to be a replacement / companion for the UI, so while you can do everything the UI does (with your own code) you can do it more efficiently!

The server portion of the LCU is the executable called LeagueClient. Client executables are usually called LeagueClientUx or LeagueClientUxRender.