[Bug] Dialogs are not hidden correctly

[schlagmichdoch]

When used with a screen reader such as orca on linux in firefox or NVDA on windows the user experience is as if all the dialogs were shown at the same time.
I guess not all of them are visible on the screen but instead of hiding them with CSS they are moved off screen or masked in anyway.
Pressing tab and shift+tab reaches controls that are supposed to be hidden.
The obvious way on how to test this is that the language selector is always reachable no matter if I press its corresponding close button or not.

Originally posted by @pvagner in #306 (comment)

[schlagmichdoch]

Apparently, the dialogs are only hidden by setting the opacity to 0. This also explains some startup issues there are with slow browsers sometimes.

@pvagner Would setting it to display: none solve this issue for screen readers like yours?

[pvagner]

@schlagmichdoch Yes, setting display: none would work for me and other screen reader users I believe. Thank you for looking into it.