Add tab-complete for commands

[Sandukhan]

Describe the bug
I recently updated from stablemaster 1.1.6 to 1.2.0 and the plugin isn't suggesting any of its commands anymore via tabcomplete.

Server version:
paper 1.8.2

StableMaster Version
1.2.0

[RobotoRaccoon]

It never did command tabcomplete to my knowledge. Feature request - not a bug