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/Plugin-ProcEnv.md

@@ -0,0 +1,22 @@
+---
+layout: default
+title: Plugin ProcEnv
+---
+
+This plugin allows prints your build time environment, which may help identify problems or reproduced the build.
+
+It prints information about the entire software build environment, any capabilities, and much more.
+The information is stored in file procenv.log in the results directory.
+It calls `procenv` command and stores its output.
+
+## Configuration
+
+You can enable the plugin using this settings:
+```python
+config_opts['plugin_conf']['procenv_enable'] = True
+config_opts['plugin_conf']['procenv_opts'] = {}
+```
+
+Available since version 1.4.18.
+
+This plugin is DISABLED by default.