Cross-link co-contributers (and this whole project) to Mobus Operandi

[MichaelRWolf]

• For frequent co-contributers,

1. Get approval to be highlighted at https://mobusoperandi.com/mobs/mobrpg.html
2. Update mob file accordingly: https://github.com/mobusoperandi/website/blob/master/mobs/mobrpg.yaml

• From our "How to contribute" page, add link to ModusOperandi: (1) to our mob page with encouragement to join us (2) to all mobs with encouragement to join other mobs, too.