add ethical ad div to nav bar

[goatlady]

Fix for JS and CSS issues on 2023 Salary Survey results page

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📚 Documentation preview 📚: https://writethedocs-www--2308.org.readthedocs.build/

[plaindocs]

What should we be seeing or not seeing here?

[goatlady]

sorry @plaindocs was trying to debug from the web interface, no action requested, forgot to mark it draft

[goatlady]

what happened: Sphinx-generated markup changed to include <p> elements inside <li> and <td> elements (server update? default settings change?)

result:

1. show/hide sub-sections JS in the left nav broke
2. default <p> margins and padding were applied to every table cell

Nothing was functionally broken - just sub-section navigation disappeared, and the data tables got REAL UGLY.

Only affected the 2023 Results page, which doesn't use the default theme CSS (which accounted for extraneous <p> elements).

Fixed page here: https://writethedocs-www--2308.org.readthedocs.build/surveys/salary-survey/2023/
Broken page here: https://www.writethedocs.org/surveys/salary-survey/2023/

[goatlady]

@plaindocs it's NOW ready for review 🙏