[Docs] Enable dark mode on documentation site

[asfimport]

pydata-sphinx-theme adds dark mode in version 0.9.0. We will need to adapt our logo (see docs). There are also some places in the docs where we may need to adjust additional CSS. See attached screenshot.

Reporter: Will Jones / @wjones127

Related issues:

• [Docs] Pin pydata-sphinx-theme to 0.8 to avoid dark mode (relates to)

Original Issue Attachments:

• Screen Shot 2022-07-20 at 3.10.51 PM.png
• Screen Shot 2022-07-20 at 3.12.18 PM.png

_{Note: This issue was originally created as ARROW-17152. Please see the migration documentation for further details.}

[AlenkaF]

This issue will be fixed with #36591 where the theme is being updated.