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-2.3.md

@@ -0,0 +1,38 @@
+---
+layout: default
+title: Release Notes 2.3
+---
+
+Released on 2020-05-22.
+
+## Mock 2.3 bugfixes:
+
+ * The `--resultdir RESULTDIR` directory is bind-mounted to bootstrap chroot, so
+   we can use `--postinstalll` even with `--bootstrap-chroot`,
+   [#564](../issues/564),
+
+ * easier configuration for `mount` plugin, [#578](../issues/578),
+
+ * mock raises better error message when `%prep` script fails during
+   dynamic_biuldrequires resolution, [#570](../issues/570),
+
+ * local mirrorlists are correctly bind-mounted to bootstrap chroot,
+   [RHBZ#1816696](https://bugzilla.redhat.com/1816696),
+
+ * traceback for invalid `getresuid()` call, [#571](../issues/571),
+
+ * use-cases with `--rootdir` and `--bootstrap-chroot` were fixed, [#560](../issues/560),
+
+ * use bootstrap (not host's) `/bin/rpm` when producing list of installed packages,
+   [PR#568](../pulls/568), (pmatilai@redhat.com),
+
+ * braced dnf variables are now expanded in repo URLs,
+   [PR#577](../pulls/577), (dmarshall@gmail.com).
+
+Following contributors contributed to this release:
+
+ * David Marshall
+ * Neal Gompa
+ * Panu Matilainen
+
+Thank you.