Add code owner ribbon to alert move

This is related to MR #13251 (comment 223259563)

Implement ribbon alert based on comment per @mvanremmerden & @marcia

Additional Requirements

• We have to update the documentation, and when doing so, adding a note in the GL versions block (the one that says "Introduced in GitLab X.Y"). Smt like:

> - [Introduced](link) in GitLab X.Y.
> - [Moved from XXX to YYY](ISSUE-LINK) in GitLab 12.4.

• Is there a way to link "Protected Branches" directly to where the user will have to change this in the UI? That would be ideal, I think. Plus, we could add a blue question mark icon linking to its documentation too