[feature] type hint in IDE

[minh-dng]

Problem / use case
Pylance cannot see the symbols in the cea pacakge. e.g. "Reactant" is not a known attribute of module "cea". reportAttributeAccessIssue

Proposed solution
I am not an expert. But I think adding a .pyi would help. This would also assist with making sure users inputting the right parameter set through @overload typing.

[TimothyEDawson]

I second this, and would also be happy to help out with the effort, time-allowing. I recently added type hints to Cantera (still a WIP), and @minh-dng is correct that stub files (.pyi extension) is a great way to add type hints to a Cython codebase.

Another option would be to migrate from the Cython syntax to the pure Python mode, although I haven't yet tried this myself so there may be limitations: https://cython.readthedocs.io/en/latest/src/tutorial/pure.html