Add example with second modal on top

[PVince81]

Add Modal example with another one on top to test focus trap.

The focus trap seems to work fine.

There's a bug though: when I submit the second dialog, instead of closing, I get this in the console:
[Vue warn]: Error in nextTick: "NotFoundError: Failed to execute 'insertBefore' on 'Node': The node before which the new node is to be inserted is not a child of this node."

This was an attempt to reproduce nextcloud/server#33637

[CarlSchwan]

I wonder if we shouldn't use the native dialog element https://developer.mozilla.org/en-US/docs/Web/HTML/Element/dialog instead of trying to mess in js the focus order

[PVince81]

wow, the dialog element looks pretty recent, I never heard of it before.

the focus trap seemed fine though and I don't think we should switch tech at this point.
would still be good to try it out separately

[PVince81]

I discovered that the case I tried to reproduce was different: it was a legacy non-vue dialog appearing on top of a vue dialog. In such case the focus trap of the parent will definitely not stop. Ideal solution: port all dialogs to Vue.

see: nextcloud/server#33516 (comment)

but if not enough we might want to add a function to pause the focus trap on the current dialog.

[PVince81]

abandoned/obsolete