Works only on 3.11.5, to make it work on other 3.11 versions, metadata.json.in has to be fixed, because development versions must be secified exactly with major.minor.point .
Everything including the close button (!) seems to work.
Keep the original formatting of messageTray.js, so changes can be determined better.
Changes to the y-values are marked with comments, changes for 3.10 compatibility not.