esengine/editrix ? reverse-engineered prompt

Build me a modular editor framework in TypeScript with a clean plugin system.

I want the core to let me create an editor, register plugins, and extend behavior without touching the base code. It should support common editor features like handling text input, selection, commands, and simple document state, plus a small demo app so I can see it working end to end.

Please set it up as a monorepo if that makes sense, with the reusable editor core separated from any example app or shared packages. Make the code easy to follow, typed well, and organized so more plugins can be added later.

If you need to look up current docs online for any tooling or best practices, go ahead. Focus on making something that feels usable, modular, and easy to grow, not just a toy example.