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-2.9.md

@@ -0,0 +1,37 @@
+---
+layout: default
+title: Release Notes 2.9
+---
+
+Released on - 2021-01-18.
+
+## Mock 2.9 new features:
+
+ * The `rpkg_preprocessor` plugin got new `force_enable` option.  This option
+   tells rpkg_preprocessor to ignore rpkg.conf and always preprocess the spec
+   file.  This is useful for testing mass package changes where it's not
+   practical to add an rpkg.conf to every package.
+
+ * The configuration mechanism was cut-out from mock, and is now newly provided
+   as new package `python3-templated-dictionary` that mock package depends on.
+
+## Mock-core-configs v33.5 fixes:
+
+ * EPEL 6 configuration was marked EOL (moved to eol/ subdirectory).
+
+ * Fedora 31 configuration is EOL, too.
+
+ * Fixed bootstrap of Fedora on Enterprise Linux 7 boxes.
+
+ * Bootstrap images defined for OpenSUSE Tumbleweed.
+
+ * RepoIDs renamed for EL8 chroots, according to real repoIDs in normal repo
+   files.
+
+The following contributors contributed to this release:
+
+ * Miroslav Suchý
+ * Neal Gompa
+ * Tom Stellard
+
+Thank you!