Consider adding support for Git Updater and RepoMan

### Description

Hello there,

Please consider adding support for Git Updater and RepoMan by adding these lines to your plugin header:

```
GitHub Plugin URI: alleyinteractive/wordpress-fieldmanager
Primary Branch: main
```

Ref: https://github.com/alleyinteractive/wordpress-fieldmanager/blob/main/fieldmanager.php

More info:

https://github.com/littlebizzy/repoman