[research] Extension with react reconciler

[HuakunShen]

I implemented two types of extensions as of now.
Template UI command design is simple. Developers don't need to know frontend, but not very flexible.
Custom UI is flexible, supports any frontend framework, but this will result in inconsistent styling, and developers have to be distracted by designing the UI instead of fully focusing on writing program logic.

Thinking about building a custom react reconciler/renderer, like react native.
Similar to how raycast extensions work.
This falls in between template UI and custom UI. Both flexible, but also limited the UI styling.

This is not necessary though, Custom UI is already like a superset, but building a custom reconciler may be fun.