Implement emoji reaction to GitLab issue for incident issues

incident.io has added a feature that will allow us to add comments to the GitLab incident issue based on an emoji reaction. This would allow us to add things to the incident.io timeline and the GitLab issue at the same time using only one reaction emoji. Thus, this feature will allow us to increase transparency to our customers about our troubleshooting information, without extra toil to post to the incident issue while also still getting everything into the incident.io timeline.

We will be enabling a workflow that causes all :pushpin: (📌) reactions be posted to the GitLab incident issue as a public comment, and any reactions with :star: (⭐) to be posted to the GitLab incident issue as an internal comment. Both reaction options will still send the information to the incident.io timeline. The message will be in the format:

User's Slack Name:

Slack Message

Unfortunately, at this time the feature will not post attached items such as screenshots.

cc/ @kkyrala