Gif

NEW:

`gif.save(..., optimize=True)` argument to shrink file size. Thanks senyai!

- New: Type Annotations
- New: `save(..., overlapping: bool)` argument for transparent plots (thanks [grburgess](https://github.com/grburgess)!)
- New: "Beating Heart" example (thanks [huang-sh](https://github.com/huang-sh)!)

- Versioning: Migrate to calver
- Removed: Altair support
- Removed: Plotly support
- Bumped: Upstream dependencies
- Tests: Simplified pytest suite

- Removed: Altair support
- Removed: Plotly support
- Bumped: Upstream dependencies
- Tests: Simplified pytest suite

- Feature: Plotly support! (Thanks alanrivetta for the suggestion!)
- Feature: seconds/milliseconds unit support in `gif.save`
- Feature: between {"frames", "startend"} support in `gif.save`
- Feature: **kwargs export/save support in `gif.options.<ploting_library>` (Thanks oaio for the PR!)
- Feature: added loop=True argument to `gif.save` (Thanks for the suggestion davidwych & sara-02!)
- Moved: matplotlib dependency is now exclusively in `pip install "gif[matplotlib]"`
- Documentation: New "love" example (Thanks huang-sh for the PR!)
- Security: Bumped pillow dependency to >=7.1.2