Add `!ListTeams` github command

[omerlh]

Some of the commands (for example, !CreateRepo, !SetRepoPermissions) require team parameters. It could help people to be able to list all teams or search for a team to find the team they needed.

[mikegrima]

The primary concern with this command is pagination. How big should the response be?

[omerlh]

I haven't thought about that, it is a challenge. We have ~20 teams, so the response could be big. What about starting with search and limiting results to the first 5 as first version? I guess this could be good enough, and no need to handle pagination.

[omerlh]

I haven't thought about that, it is a challenge. We have ~20 teams, so the response could be big. What about starting with search and limiting results to the first 5 as first version? I guess this could be good enough, and no need to handle pagination.