chore: update release please config for mm plugins (#111)

## Description

Fix the mm release please config for the plugin package.

## Related Issue

Fixes #N/A

## Type of change

- [ ] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [X] Other (security config, docs update, etc)

## Checklist before merging

- [X] Test, docs, adr added or updated as needed
- [X] [Contributor Guide
Steps](https://github.com/defenseunicorns/uds-package-mattermost/blob/main/CONTRIBUTING.md#developer-workflow)
followed

release-please-config.json

@@ -16,6 +16,7 @@
       "extra-files": [
         "bundle/uds-bundle.yaml",
         "tasks/publish.yaml",
+        "plugins/zarf.yaml",
         "zarf.yaml"
       ]
     }