fix typos

[elpekenin]

Fixes #17

Double-checked all the fields in Card, will look for similar errors on other types later.

Side note: Python 3.8 support was dropped last October, and this year 3.9 will also be dropped. Shall i also update the project's metadata to bump the required version to 3.10? It would also allow using newer syntax, like list[int] | None instead of requiring imports of List and Optional from the typing module