feat: Add universal navigation bar

[xeniape]

This PR adds the universal navigation bar, similar to the one in the HUB, mimicking its design and functionality, but adjusted some minor things compared to the HUB version:

• GitHub link opens in a new tab (since it does not have the navigation bar to navigate back)
• Clicking outside of the drop down menu, closes it
• If the drop down menu is open and screen size changes to the desktop version, it does not display the lingering drop down menu
• Change "Docs" menu item names to "Documentation"
• Remove grey host labels from menu items in desktop version

[NickLarsenNZ]

Do you have a screenshot available? Or can it be deployed somewhere?

[xeniape]

Do you have a screenshot available? Or can it be deployed somewhere?

If it's not too much to ask I would prefer if you could build it and try it out (to catch things that don't work). For that you would go into the documentation repository, create a symlink ui to the local checkouted branch here (move the git module temporarily), and use the make build-truly-local command. But I can also attach a screenshot in a bit.

[xeniape]

Basically the same as in https://hub.stackable.tech/ but with the adjustments mentioned above

[Techassi]

Having this right above the logo of the docs header looks really weird/overloaded. I would remove one of the two (most likely the one from the docs header as this universal nav bar seems to be the way forward).

[xeniape]

Agreed, but would do that as part of another PR to keep the scope about the universal header only.

[NickLarsenNZ]

Approved based on resolved comments.