Add overlay between calendar and open simple editor

[ChristophWurst]

Is your feature request related to a problem? Please describe.

As a Nextcloud user I don't want other calendar elements to be clickable while the simple editor is open.

E.g.

1. Open my calendar with existing events
2. Click on event a -> see the simple editor for a
3. Click on event b -> see the simple editor for b

Describe the solution you'd like

1. Open my calendar with existing events
2. Click on event a -> see the simple editor for a
3. I'm not able to click anything outside of the simple editor within the view of the calendar. This is similar to modals.

Describe alternatives you've considered

#5513

Additional context

N/a

[nimishavijay]

Ideal solution:

• clicking anywhere outside of the editor when it is in edit mode does nothing (editor stays open in edit mode)
• clicking anywhere outside of the editor when it is in view mode closes the editor and does not open anything else