`extra.css` specifies a background color for `td` and `th`. I believe it is used only for the `readthedocs` theme, and I do not see why it is needed there; it slightly interferes with dark mode. Comment it out rather than deleting it, just in case a need is established for it.
Color the top bar for `zensical`.
`mkdocs` theme has a weird problem described in its yml file. There is a workaround, but I'm not comitted to it, so make it available but don't use it yet.
oleibman