config_writeback 1.1.x-dev

Initial release.

- Adds a "Git Writeback" tab on the Configuration Synchronization page
(/admin/config/development/configuration).
- Exports active configuration, commits it to a timestamped feature branch,
and pushes it to a git remote (Bitbucket or GitHub).
- Shows a diff preview before pushing, and generates a "Create Pull Request"
link automatically.
- Supports locking the target branch and webroot per environment via
settings.local.php.
- Integrates with Config Ignore (if installed) to include/exclude
environment-specific configuration.
- No credentials are stored; tokens are used only for the duration of the
git operation.