KeyboardApi methods return Result<T> instead of Option<T>

[irobot]

• Introduce a unified Error enum.
• Update all KeyboardApi methods to return Result<T>.
• Implement From<Error> for pyo3::PyErr to support Python bindings.

BREAKING CHANGE: KeyboardApi methods now return Result<T> instead of Option<T>

[srwi]

Thank you for the PR! I haven't had the time to look into it. Will do so in the coming days!

[irobot]

Thank you, and no worries! I know it looks like a lot, but the bulk of it is simply replacing Option<> with Result<>. The rest is just error formatting. Whenever you get to it, do let me know if you have questions.

[srwi]

Finally got to have a closer look. I like the changes. Thanks again for the contribution! 🙂