Dark mode: invert some images

[hugovk]

As detailed at https://discuss.python.org/t/styling-of-peps/13270/25?u=hugovk and https://discuss.python.org/t/styling-of-peps/13270/26?u=hugovk, a number of images need adapting to display in dark mode.

Use CSS to invert those images in PEP-0001 and marked 🔄 above.

[encukou]

Thank you for implementing this!
As a PEP author (and reader of the sources), I'd appreciate if the class was called e.g. invert-in-dark-mode.

(edited to add:) I work in light mode so the class won't do anything for me. With dark-mode in the name the reason for the class would be obvious.

[hugovk]

Thank you for implementing this! As a PEP author (and reader of the sources), I'd appreciate if the class was called e.g. invert-in-dark-mode.

(edited to add:) I work in light mode so the class won't do anything for me. With dark-mode in the name the reason for the class would be obvious.

Updated!

[CAM-Gerlach]

LGTM (at least per my previous investigation and spot checks of this one). Thanks, @hugovk

[AA-Turner]

87a35b1fea as proposed uses pure reST :class: options rather than the .. rst-class extension -- purely an implementation change.

A