Adds Event polyfill for IE

What does this MR do?

Adds a polyfill for new Event for IE 11 https://developer.mozilla.org/en-US/docs/Web/API/Event/Event

We use new Event in at least 8 places, causing a lot of features to not work on IE11

Screen_Recording_2017-09-08_at_04.48_PM

Are there points in the code the reviewer needs to double check?

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Review
  • Has been reviewed by Frontend
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together

What are the relevant issue numbers?

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/37633 https://gitlab.com/gitlab-org/gitlab-ce/issues/37139