8.5
ci: Only run documentation/link tests on a single job.
docs: Convert reST index pages to Markdown.
docs: Update Ruff badge and links.
gear_menu: Rename "Manage streams" -> "Stream settings".
codespell: Fix typos caught by codespell.
docs: Format Markdown with Prettier.
docs: Fix outdated number of backend tests.
node_tests: Move to web/tests.
docs: Rename "private message" -> "direct message".
models: Rename zerver/models.py to zerver/models/__init__.py.
docs: Clean redundant relative links.