Post comment from Slack to Trello card

Keeps track of the last trello card mentioned, and when someone says "@bots add Trello comment: [insert comment here]" the comment will be posted to that card
Readme:

For this to work, @bots needs to be in your channel, you can invite us with /invite @bots

This sketch monitors Slack for mentions of Trello cards, when it spots one it will respond with a :robot_face: emoji reaction.

Later, you can ask BOTS to add a comment to the card, e.g. @bots: add trello comment: We've decided to go with blue and this sketch will post a comment to the trello card including the requested text (We've decided to go with blue) and permalink to the message in Slack. If successful it should add the ✅ reaction to the message.