Reactive I/O

Currently in the early development phase; do not use in production.

Roadmap:

• RxVar[T]: variable
• RxResult[*Ps, T]: function result, bound to reactive args
• Rx{Function,Method}: returns RxResult, can watch when called
• (mk)docs
• github actions
• RxAttr[T]: descriptor attribute / field
• RxType: custom rx type base: reactive attrs, methods, properties and lifecycle
• Rx{Bool,Int,Float,Str,...}: reactie builtin types
• Rx{Tuple,List,Set,Dict,...}: reactive builtin collections
• reactive(...): central Rx* construction for (builtin) types, functions, etc.
• Rx{File,Signal,Process,Socket,...}: reactive IO (state)
• dataclasses integration
• (optional) python-attrs integration
• (optional) pydantic integration