Improve documentation for this package

[arnavb]

Currently, this package's documentation is limited to the README file provided in the repository/distributed bundle. This isn't useful for people programming in an editor or using the help function. The following changes need to be made:

• Add a changelog of changes during each release.
• Add PEP 526-style instance variable annotations for each of the public fields on the Pokemon object.
• Add docstrings to all (if possible) modules/classes/methods/attributes.
• (Optional) Host generated documentation on a website such as readthedocs.

This will probably be pushed as a minor version update since it doesn't change the API of the package.

[Acryptarch]

You have typo in your readme. I think you say "intt" instead of "int". Idk if this is important enough for you to care about though.

[arnavb]

@Acryptarch I'll fix that in the next documentation release.