It turns out the only code path taken through it was a trivial loop.

- Updated theme sections to mark mkdocs and readthedocs as official themes
- Added separate install instructions for both themes
- Removed references to built-in themes

- Replace "built in themes" with "official themes"
- Remove ProperDocs Themes wiki link

When highlightjs is disabled, some HTML elements don't exist. But the code didn't expect this and had an error, interrupting the entire action of toggling dark mode.

We must not attempt to get the file name of stdin (the current error) and we also must not try to re-read it.

Now that this case is handled specifically at `serve`, we don't need to generally expect closed files in `load_config` - it was a workaround and an insufficient one at that.

…age (#53)

The commit squidfunk/mkdocs-material@51d9b76 made this environment unusable - it's always set and there's no reasonable way to detect whether it was actually set on the command line.

Users will unfortunately run into a new nuisance even if they previously set our variable.

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Also, add a direct mention how to suppress the warning.

Now that we've had to change this variable once, it's nice to give users a direct way to get rid of this.

I don't know how I was thinking the piece of code `if log.getEffectiveLevel() > logging.DEBUG` was supposed to work. It doesn't achieve anything like the comment is saying "`Populated only if `validation: {anchors: info}` (or greater) is set.`" - but it does disable anchor validation under `--verbose`.