We're migrating to using the cleaner zulip.com domain, which involves
changing all of our links from ReadTheDocs and other places to point
to the cleaner URL.
I only renamed references that I thought were absolutely necessary
and only if the resulting sentence structure wasn't awkward.
If the renaming resulted in awkward structure, I replaced the term
"webhook" with "integration" (but only in some very obvious cases).
Fixes#9500.
This commit helps reduce clutter on the navigation sidebar.
Creates new directories and moves relevant files into them.
Modifies index.rst, symlinks, and image paths accordingly.
This commit also enables expandable/collapsible navigation items,
renames files in docs/development and docs/production,
modifies /tools/test-documentation so that it overrides a theme setting,
Also updates links to other docs, file paths in the codebase that point
to developer documents, and files that should be excluded from lint tests.
Note that this commit does not update direct links to
zulip.readthedocs.io in the codebase; those will be resolved in an
upcoming follow-up commit (it'll be easier to verify all the links
once this is merged and ReadTheDocs is updated).
Fixes#5265.