Establish menu item capitalization guidelines and apply them across

We still need to establish some capitalization guidelines and apply them to the project as a whole. Again here the secondary navigation uses titlecase, while the individual pages you land on use sentence case.

An example from the forums:

• Guidelines leads to a page called "Forum Guidelines".
• Welcome to Support leads to "Welcome to the WordPress.org support forums"
• Get Involved leads to "Support Handbook"

We will want to be editorial in the breadcrumb links, so it's okay to shorten titles if need be. But we should strive to have the same title at the destination, as is in the link, and we should have the same capitalization.

Firstly we should decide on whether to use sentence case or title case for titles across the site. After that, we can establish and applyl those guidelines, perhaps in a new "manual of style".

Suggested guidelines:

• Use the generally decided upon case for titles, sentence or title, not both.
• When possible, use the same title for the link as the title for the page itself. Or vice versa, rename pages to be shorter if the navigation link needs to be shorter.
• In all cases, and especially for the edge cases when titles diverge, ensure proper capitalization.

Also worth fixing here for "My Favorites" vs. "Submit a plugin"

No files, tests, or entry points are named; begin by reviewing the site's navigation and destination titles described in the issue, including the forums examples. A decision on sentence versus title case, a documented style guideline, and consistent capitalization for the cited links and pages would define done.