Manim v0.20.1 发布

<!-- Release notes generated using configuration in .github/release.yml at main -->

See details at https://docs.manim.community/en/stable/changelog/0.20.1-changelog.html.

## What's Changed

### Enhancements 🚀

* Cleanup `TipableVMobject`: avoid mutable default and fix `assign_tip_attr` typo by @josiest in https://github.com/ManimCommunity/manim/pull/4503

* enhancement: optimize Docker image build and runtime footprint by @behackl in https://github.com/ManimCommunity/manim/pull/4604

### Bug Fixes 🐛

* fix: MathTex double-brace splitting no longer fires on natural LaTeX `}}` by @behackl in https://github.com/ManimCommunity/manim/pull/4602

* Fix creation or animation of a zero-length `DashedLine` by @SORVER in https://github.com/ManimCommunity/manim/pull/4606

* Fix moving-object detection for nested AnimationGroups with z-indexed mobjects by @Merzlikin-Matvey in https://github.com/ManimCommunity/manim/pull/4389

* Fix unintended propagation of `kwargs` in `LaggedStartMap` by @irvanalhaq9 in https://github.com/ManimCommunity/manim/pull/4613

### Documentation 📚

* Documentation: manual installation of manim as a local package by @u7920349 in https://github.com/ManimCommunity/manim/pull/4456

* Add alt text to all images in `README.md` by @VerisimilitudeX in https://github.com/ManimCommunity/manim/pull/4064

### Code Quality & Refactoring 🧹

* Fix publish release workflow by @behackl in https://github.com/ManimCommunity/manim/pull/4600

* Silence pydub ffmpeg/avconv import warning when ffmpeg CLI is absent by @behackl in https://github.com/ManimCommunity/manim/pull/4603

### Type Hints 📝

* Add type annotations to `manim/_config/utils.py` by @henrikmidtiby in https://github.com/ManimCommunity/manim/pull/4230

## New Contributors

* @SORVER made their first contribution in https://github.com/ManimCommunity/manim/pull/4606

* @josiest made their first contribution in https://github.com/ManimCommunity/manim/pull/4503

* @u7920349 made their first contribution in https://github.com/ManimCommunity/manim/pull/4456

* @Merzlikin-Matvey made their first contribution in https://github.com/ManimCommunity/manim/pull/4389

* @VerisimilitudeX made their first contribution in https://github.com/ManimCommunity/manim/pull/4064

**Full Changelog**: https://github.com/ManimCommunity/manim/compare/v0.20.0...v0.20.1