[Docs] Add LinkedIn social link and fix top nav scaling problems

[ianmcook]

Describe the bug, including details regarding any error messages, version, and platform.

We should add a LinkedIn icon social link to the main docs pages. We created a Linkedin page for the project in mid-2024. It has been in active use since then. This month, we added a LinkedIn follow button to the website homepage. So it makes sense to add a LinkedIn icon social link to the main docs pages alongside the X icon social link.

However, this will increase the width of the contents in the top nav. As is, the layout of the top nav is already broken on smaller screens, with the items wrapping onto multiple lines at screen widths above 960px (which is the breakpoint at which the PyData Sphinx page layout changes and the top nav items move into a modal side nav) and below 1200px. So we should also fix this problem at the same time.

Component(s)

Documentation

[ianmcook]

Resolved by #45228