Consider adding support for Git Updater and RepoMan

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