test(a11y): Changing the header components order

[mfranzke]

Currently the header components order is a little bit weird to screenreader users, as the navigation comes before the logo. This should get switched.

Previously we've chosen this order due to CSS simplicity, but now we could use the all new :has-selector (or even better flex or grid) to achieve our expectations regarding the header styling.

WCAG 1.3.2 Meaningful Sequence (Level A)