Prepared new release, v0.16.0

[behackl]

Preparation of new release.

Link to changelog: https://manimce--2863.org.readthedocs.build/en/2863/changelog/0.16.0-changelog.html

[behackl]

The changelog is in a pretty good shape in my opinion, the release is almost fully prepared and this is ready to be reviewed:

• There was a typo in the title of Made FFmpeg executable path configurable #2667 (which is why pre-commit.ci fails), the fix will be reflected in the next (and likely last) changelog generation pass,
• and Enabled filling color by value for :class:.OpenGLSurface, replaced colors keyword argument of :meth:.Surface.set_fill_by_value with colorscale #2186 is not included yet (needs a cross-review of my changes).

[ad-chaos]

👌