- Updated editor, and other area, styles to look okay in dark mode.
- Used tinyMCE theme generator to create dark mode theme.
- Updated tinymce to latest 4x version.
- Most elements done, but still need to do editors, tables and final
pass.
- Toggled only by quick js check at the moment, checking via css media
query. Need to make into user-preference toggle.
For #1234
Optionally we could consider removing the rule at line 274. This doesn't handle multiple layers of nested lists and would be better covered by the generic rule which checks for an `ol` or `ul` nested inside a `li` which is how MarkDown renders nested lists as HTML.
