Previously the title for all pages of the user and API documentation was
just "Zulip", which does not only bad for UX but also for accessibility.
We were already extracting the title from the Markdown for the og:title
tag, so we just need to set the <title> tag.
Since our documentation fetches pages with Ajax if you have JavaScript
enabled, we also need to save the titles in the article cache.
Part of #15948.
Three reasons:
1. The sliding was disorienting.
2. The collapsing disallowed searching for other pages with Ctrl+F.
3. The collapsing mechanism wasn't accessible (not usable with the
keyboard / no ARIA tags).
Tweaked by tabbott to center the left sidebar on the selected page.
Part of #15948.
We now prevent these variations:
* <hr/>
* <hr />
* <br/>
* <br />
We could enforce similar consistency for other void
tags, if we wished, but these two are particularly
prevalent.
Gittenburg
Steve Howell
Anders Kaseorg
Rishi Gupta
Akash Nimare
Lyla Fischer