This adds a new docs page covering how to manage SSL/TLS certificates

and CA bundles. As of Review Board 8, these need to be configured

manually on the filesystem. This guide walks through how to do that, and

the various SSL options available.
Since there's a lot of terms thrown around, the glossary has been

updated to flesh out these terms and link back to this page.
In the future, this page will be a good place to document the cert

configuration UI and cert synchronization, once that's been written.

Checked for obvious spelling, link, or build errors. Ran it through

Claude to check for any notable issues.