Added Docstring/Example for :meth:always_redraw

[JasonGrace2282]

Overview: What does this pull request change?

• Added an example to always_redraw
• Changed lambda m: mob.become(func()) to lambda _: mob.become(func()) for clarity

Motivation and Explanation: Why and how do your changes improve the library?

There wasn't much of an example for always_redraw, which might've helped with learning how to use updators and such.

Links to added or changed documentation pages

https://manimce--3312.org.readthedocs.build/en/3312/reference/manim.animation.updaters.mobject_update_utils.html

Reviewer Checklist

• The PR title is descriptive enough for the changelog, and the PR is labeled correctly
• If applicable: newly added non-private functions and classes have a docstring including a short summary and a PARAMETERS section
• If applicable: newly added functions and classes are tested

[jsonvillanueva]

Thanks for the doc snippet! The TangentAnimation gives two good examples of always_redraw. I would only shorten the run_time to make the animation render quicker during our Read the Docs (RTD) builds and also make the video size a bit smaller (most docs animations are short for this reason).

[JasonGrace2282]

@jsonvillanueva I took your suggestion. Any other commends or todo's?

[behackl]

Looking good, thank you for your efforts! I've left some more comments, please have a look.

[behackl]

while we are at it, we could probably also add a type hint for func, it should be something like Callable[[], Mobject] (with Callable from collections.abc) I guess.

[JasonGrace2282]

@behackl I updated my PR to reflect your suggestions.

[behackl]

Sorry, it seems I failed to comment one final suggestion that I had that added an explicit parameter description -- and while fixing that, I also saw that the return type of the function was missing.

After this, I'm happy and ready to merge though; thank you!

[JasonGrace2282]

@behackl Implemented your suggestions!

[behackl]

Thanks again!