Refactor code and add tests

[bawahakim]

Realized the package did not have tests, so wanted to take a stab at it. This brought me down a long rabbit hole of refactoring. Hope you don't mind! I did use a bit of LLM for the refactoring, comments and boilerplate

This PR should not bring any breaking changes, as I left the original public functions that were used (either whitelist, commands, or hooks) and wrapped it with the new TypeGenerator class

Added github workflow to run the tests. I also added default linter from bench and linted the package

Note: I needed to add a new global include_custom_doctypes, otherwise it would create a test doctype in code and made cleanup a bit messy. It defaults to false to avoid breaking changes. Similarly added base_output_path but as a hidden field, which defaults to ../apps, which was necessary to keep tests clean and output generation to /tmp, also non breaking.

Questions:

1. create_type_definition_file seems to be called on doctype update. Would it make sense to rename it update_type_definition_file? I did so in the new class
2. create_type_definition_file has a few differences from the generate method:

• it checks if frappe is migrating, if so returns
• it checks if the change is coming from frappe or erpnext, if so returns
  Is there a reason to have this only in this method and not the generator methods?