enhance: Add comprehensive .gitignore for deb-mock project

- Add mock-specific build artifacts (chroot/, mock-*, mockroot/)
- Include package build files (*.deb, *.changes, *.buildinfo)
- Add development tools (.coverage, .pytest_cache, .tox)
- Include system files (.DS_Store, Thumbs.db, ._*)
- Add temporary and backup files (*.tmp, *.bak, *.backup)
- Include local configuration overrides (config.local.yaml, .env.local)
- Add test artifacts and documentation builds
- Comprehensive coverage for Python build system project

This ensures build artifacts, chroot environments, and development
tools are properly ignored in version control.

docs/Release-Notes-3.3.md

@@ -0,0 +1,15 @@
+---
+layout: default
+title: Release Notes - Mock v3.3
+---
+
+Released on 2022-10-17.
+
+## Mock v3.3 bugfixes:
+
+The fix for `--list-chroots` and `simple_load_config()` from
+[v3.2](Release-Notes-3.2) disallowed running Mock under the `root` user.  Since
+this is still a common practice [issue#990][], we relaxed the rule and we only
+raise a warning if `simple_load_config()` is executed by `root`.
+
+[issue#990]: https://github.com/rpm-software-management/mock/issues/990