[Dev] use type hint and type checker

[lisphilar]

Checkbox

• I agree to follow code of conduct and to engage in discussion actively.
• I have confirmed I will follow and update contribution guideline.

Issues of the current workflow

Type hints are documented in docstings and un-analyzable with type checker.

Action items

• use type hints in APIs users will call: downloading
• use type hints in APIs users will call: dynamics
• use type hints in APIs users will call: engineering
• use type hints in APIs users will call: gis
• use type hints in APIs users will call: science
• use type hints in APIs users will call: util
• use type hints in APIs users will call: metadata
• use type hints in internal classes and methods: downloading
• use type hints in internal classes and methods: dynamics
• use type hints in internal classes and methods: engineering
• use type hints in internal classes and methods: gis
• use type hints in internal classes and methods: science
• use type hints in internal classes and methods: util
• use type hints in internal classes and methods: metadata
• use type checker: e.g. pyright, mypy, pytype
• include py.typed in folders

Additional Context

To keep backward compatibility, from __future__ import annotations and typing_extension library may be used.

[lisphilar]

We may need the sphinx.ext.autodoc.typehints extension to show types in documentation.
https://github.com/tox-dev/sphinx-autodoc-typehints

[lisphilar]

sphinx.ext.autodoc.typehints will be used in documentation workflow with #1285.

[lisphilar]

With "1286,

• use type hints in APIs users will call: dynamics
• use pyright as type checker
• fix/suppress errors of type hints found by pyright
• update intersphinx mapping to link with numpy and matplotlib in docs/conf.py

[lisphilar]

py.typed should be included.

https://blog.whtsky.me/tech/2021/dont-forget-py.typed-for-your-typed-python-package/