Ternary-diagram

**Full Changelog**: https://github.com/yu9824/ternary_diagram/compare/v3.0.1...v3.1.0

- Resolve 10 (Create `fill` argument in `TernaryDiagram.contour`).
- Resolve 11 (Create `auto_latex_notation` argument in `TernaryDiagram`).
- Update documentation.
- Update docstrings and typings.

- Fix bugs.
- Add typings.

Conda-forge released.

Mainly to rebuild v2.1.0.

- Update .gitignore.

Specification change.
- Change the objects returned by scatter, contour, plot, and annotate (the objects returned by the corresponding matplotlib functions).
- Definition of `_draw_colorbar` function and `TernaryDiagram.colorbar` function.
- Added `flag_cbar` as an argument to indicate whether to draw colorbar in scatter and contour.