Currently MinervaNeue doesn't provide a visual focus feedback to keyboard/assistive technology users.
This is an accessibility anti-pattern as described in http://www.outlinenone.com/
It also isn't relying on mediawiki.ui-input (any more?), so let's rebuild the focus styles according to UI-Standardization component treatment to resolve the focus issue.
- No visual change in default appearance
- Add standard focus treatment
Additionally let's care for
- cleaning up CSS a bit (removing old Nokia60 override, bring properties in order etc.)
- remove the focus flash (https://phabricator.wikimedia.org/T218154#5079887)