- Adds desktop/web instructions.
- Adds #inbox relative link for logged-in users.
- Moves Inbox up in the left sidebar just under "Reading strategies".
- Moves Inbox article content to Markdown include.
- Adds "From the Inbox view" section to "Finding a topic to read",
"Getting started with Zulip", and "Reading strategies".
- Documents Inbox as a new option for the default web app view.
- Removes unused Markdown link.
- Tweaks subheading to better match help center patterns.
- Add Inbox option in "Configure default settings for new users".
- Adds new tabbed section and instructions for marking messages as
read and reading topics via the Inbox view.
Fixes#26903.
Co-authored-by: Alya Abbott <alya@zulip.com>
These files are not Jinja2 templates, so there's no reason that they needed
to be inside `templates/zerver`. Moving them to the top level reflects their
importance and also makes it feel nicer to work on editing the help center content,
without it being unnecessary buried deep in the codebase.