Fix navigation on smaller screens

[bartaz]

Done

Fixes top navigation on medium screens (tablets) by properly adjusting breakpoint value, passing it to global nav, and adding medium screen column values.

Before:

After

QA

• Check out this feature branch
• Run the site using the command ./run serve
• View the site locally in your web browser at: http://0.0.0.0:8043/
• Run through the following QA steps
• Check if top navigation displays correctly on various screen sizes (from mobile, through tablet, up to desktop)

[webteam-app]

Demo starting at https://anbox-cloud-io-329.demos.haus

[edlerd]

LGTM, one tiny nitpick. Feel free to merge as is.