sg: Add `sg rfc [list|search|open]` commands
Created by: mrnugget
Demo video:
https://user-images.githubusercontent.com/1185253/125973447-ee13e2be-b644-44ae-a910-7225cf13403b.mp4
Created by: mrnugget
Demo video:
https://user-images.githubusercontent.com/1185253/125973447-ee13e2be-b644-44ae-a910-7225cf13403b.mp4