Enhancement: Accessibility

Several accessibility improvements have been made, most notably in regards to color contrasts and outlines when navigating via keyboard.

https://github.com/owncloud/web/pull/11315
https://github.com/owncloud/web/pull/11331
https://github.com/owncloud/web/pull/11320
https://github.com/owncloud/web/issues/10730
https://github.com/owncloud/web/issues/10726
https://github.com/owncloud/web/issues/10735
