Typing progress tracker

A pull request for this has already been merged.

• #4497 by @henrikmidtiby — merged

This issue is meant to track progress related to adding type hints to the library.

Fixes:
- https://github.com/ManimCommunity/manim/issues/52
- https://github.com/ManimCommunity/manim/issues/2121

## Progress (layout subject to changes):

- [x] `_config`: https://github.com/ManimCommunity/manim/pull/3440
- [ ] `animation`: https://github.com/ManimCommunity/manim/pull/3457
- [ ] `camera`
- [x] `cli`: https://github.com/ManimCommunity/manim/pull/3988
- [ ] `gui`
- [ ] `mobject`
- [x] `mobject.geometry`
- [ ] `mobject.graphing`
- [ ] `mobject.opengl`
- [ ] `mobject.svg`
- [ ] `mobject.text`
- [ ] `mobject.three_d`
- [ ] `mobject.types`
- [ ] `mobject.*.py`
- [x] `opengl`
- [x] `plugins`: https://github.com/ManimCommunity/manim/pull/4006
- [ ] `renderer` (on hold due to the experimental branch)
- [ ] `scene`
- [ ] `utils`
- [x] `__main__.py`: https://github.com/ManimCommunity/manim/pull/4007
- [x] `constants.py`: https://github.com/ManimCommunity/manim/pull/3086
- [x] `typing.py`

## Contributing

Contribution guidelines can be found here (TODO).

This issue can be used for any questions (Discord is good place as well).

When starting working on a new module, you can tweak the `ignore_errors` value in the `mypy.ini` configuration file:

https://github.com/ManimCommunity/manim/blob/c6450b21c7d37d97c27beaf39faf2758da03bf8e/.mypy.ini#L4-L6

Review the progress list in this issue and choose an unfinished module such as camera, gui, mobject, scene, or utils. Start by reading that module and the referenced .mypy.ini ignore_errors setting, then run mypy for the selected area. Done means the module has type hints and its progress entry can be updated.

Written by the indexing model from the issue text.