ci: add dangerfiles for mr hygiene

Why is this change being made

For new MRs in this project, we want a warning to fire for missing work type labels. Work type labels are used to evaluate the type of work the team is doing. This information is used to understand where we are investing, where to put more resources, how to plan for new features etc.

Relates to #650 (closed)

Testing notes

Tested with a branch associated with an issue !1002 (closed), and the MR is also associated with the issue !1001 (closed). The danger-review bot ran for the reviewer roulette in both scenarios, but it was not possible to test the warning.

With this MR the branch is not associated to an issue and the danger-review throws the warning.

Results

After this change, the bot will display the warning to add a work type label, as the following image