chore: add publish flag

[ronjaquensel]

What this PR changes/adds

Adds a publish flag to the plugin. The flag doesn't have any effect yet.

Why it does that

Once #67 is merged, publications will be added automatically and the publish flag can be used to disable this for a module. To ease the process of merging the changes in all repositories, the publish flag is added beforehand.

Checklist

• added appropriate tests?
• performed checkstyle check locally?
• added/updated copyright headers?
• documented public classes/methods?
• added/updated relevant documentation?
• assigned appropriate label? (exclude from changelog with label no-changelog)
• formatted title correctly? (take a look at the CONTRIBUTING and Etiquette for pull requests for details)