Creates new help article for supported web browsers. Also updates
links in the `/apps` landing page as well as the unsupported-browser
template and the `set-up-your-account` article.
Fixes#14732.
Removes the default title element of "Zulip" from `base.html` and
the default meta-description sentence from `meta_tags.html`. Also
removes default open graph metadata.
For portico templates that would would fail tests, set both
`PAGE_TITLE` and `PAGE_DESCRIPTION` variables with appropriate
content.
Co-authored-by: Alya Abbott <alya@zulip.com>