Fix list-style for bibliographies in dark mode

[goerz]

Cf. https://github.com/JuliaDocs/DocumenterCitations.jl/pull/70

You'd still have to follow up with modifying any existing citations.css in your gh-pages.

Closes #3704

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 98.35%. Comparing base (a39e241) to head (582f976).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #3706 +/- ## ======================================= Coverage 98.35% 98.35% ======================================= Files 43 43 Lines 5707 5707 ======================================= Hits 5613 5613 Misses 94 94 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.

[odow]

Thanks @goerz

[jd-foster]

Thank you @goerz !