Sphinx extension not compatible with python 3.13

[jacobtylerwalls]

Build fails on python 3.13 with the issue described here:
https://stackoverflow.com/questions/79144437/how-to-resolve-no-module-named-imghdr-error-in-python-3-13-with-tweepy

Some questions to answer:

• do we need that plugin
• can we upgrade
• any other workarounds?

[ekansa]

@jacobtylerwalls thanks for catching this. I'll see if we can drop that plugin without bad impacts first. I'd rather reduce the number of dependencies to make this easier to maintain