Proposal to refactor Reader and Type classes

[Irineu333]

Description

A proposal to improve the Type class. It also extracts state and type reading logic for extensions.

I didn't send it directly in a commit to #100, because it's a proposal. We may not go through with it.

Improvements

• Refactor Type enum class to selead class
• Simplify Reader class
• Improve and extract node read logic for extensions

Fixes

• Add custom checkable support #111