Add emojis for the severity levels of Pull Requests

[Tobbse]

Is your feature request related to a problem? Please describe.
Distinguishing urgent Pull Requests from trivial ones is currently not easily possible.

Describe the solution you'd like
It would be awesome if the bot could add emojis (we already have Jira-style emojis in the InnoGames Slack workspace) to published PR messages in order to see how urgently a PR needs to be reviewed. For that we could fetch the severity level from a Jira ticket associated with the PR. I am not sure if that is feasible or easily possible.

Describe alternatives you've considered
If the connection to Jira isn't (easily) possible we could listen to keywords in the title of the PR maybe, if it's urgent..? But then again, adding an emoji manually in that case seems like the same effort.