[BUG] `Str` enums are incorrectly formatted in Python>=3.11

[jeertmans]

Discussed in #253

^{Originally posted by alexanderskulikov August 23, 2023}
Hi!

Could you please help me to resolve an issue with converting to html? Just recently, everything was working fine with that, but now nothing is shown in the resulting html file. Yesterday I upgraded to the latest version of manim-slides, though I'm not sure that this is the reason. To be more specific, when I take the basic example source code (from this page) and run manim example.py BasicExample and then manim-slides convert BasicExample scene.html --open, then this is what I see:

Am I doing something wrong?

Best,
Sasha