Add list of actively developed alternatives in light of soft EOL

[alexweissman]

Would you consider adding a list of suggested alternatives to the readme, in light of Huge's soft EOL?

Obviously I'm going to recommend my own project, UserFrosting, but there are other good projects out there as well:

• Laravel Voyager
• Cartalyst Sentinel
• jwt-auth for Laravel

All of these projects are built with, or integrate with, the major modern PHP frameworks. I'd be happy to submit a pull request if this is something you'd be interested in.