Accessibility issues

[CarlSchwan]

Unorganized dump of accessibility issues I found when doing nextcloud/server#31584

Focus handling

• Focus effect is not big enough against the element beside it (1.13) and is inexistent when the category is (selected style == focus style)
  

• Same issue with setting category
  

• Avatar can be focused but when clicking on it nothing happens (probably shouldn't be focusable at all)

• Upload button focus is not big enough
  

• Various text fiels don't have a visible label
  

• Warning button can't be focused
  

• Add groups button doesn't have popover and aria-label is "Actions" instead of "Create a Group"