Popover has lower z-index than resize-handle

[johanrd]

https://limber.glimdown.com/edit?c=Q&forceEditor=true&format=gjs

Two different ways to solve this:

1. johanrd@c751df1 – this is perhaps to prefer (if there are no remembered reason for the z-10, of course)
2. johanrd@b2e7f77 – this is just to point to the where the other z-index is. Could perhaps be solved by setting class="z-20" on the menu component, and spread it with ...attributes.

[NullVoxPopuli]

Fixed in #1642