Habitat: [web ui] Reduce fixed header size & add GitHub tab on it

[apriofrost]

The current fixed header on the site takes too much real estate on the screen (about 122 px in height). See the screenshot from @ShalokShalom 's 15.4- inch screen.

The suggested design is to make it shorter (about 77px in height). See the screenshot from the mockup:

Another suggested improvement on the design is to replace the current GitHub ribbon with the tab style. So that it can fit into the fixed header and always available.

To inspect the mockup: https://chef.invisionapp.com/d/main#/console/9499228/229572977/preview

[ryankeairns]

We might also want to reduce the logo size when it's fixed... it's hugging rather close to the bottom of the fixed nav background.

[apriofrost]

@ryankeairns Yeah. For sure! (as a designer from agencies, I often struggled with the logo being not big enough from the clients' point of view) :D

[ryankeairns]

Haha!

https://youtu.be/5AxwaszFbDw

[rsertelon]

@apriofrost @ryankeairns @eeyun it seems that there's no more fixed header on the website and bldr. Is this issue still a thing? :)

[apriofrost]

I think we turned off the fixed header off after the Builder launch on Oct 9th. There were some complaints about it covering too much content underneath.

[ryankeairns]

The fixed header was removed here: https://github.com/habitat-sh/habitat/pull/3849