Need FAQ in github-bot in docs

[nixorokish]

We need a FAQ for the github bot:

• Add GitPOAP bot trufflesuite/truffle#5285 (comment)
  another example:
  

• Another Item: That there is no cost associated with onboarding onto GitPOAP / having us do your designs

[colfax23]

Great call. I think another thing worth noting explicitly in an FAQ section is that we will not be posting on historical PRs, only new ones after the bot is configured.