Update header component

[thatbudakguy]

This updates the designs to match the v.2 header component in Figma.

The templates were updated to make the content as close as possible to what's currently in Figma.

Closes #92

[jcoyne]

Where does this occur?

[thatbudakguy]

component-library/header/with_navigation_links.html

Line 223 in a13b573

<hr class="d-md-none text-white vw-100 my-0" />

and

component-library/header/with_navigation_links.html

Line 308 in a13b573

<hr class="d-md-none text-white vw-100 my-0" />

[jcoyne]

This is a lot to digest at once. Is there any way to break it up into smaller pieces of work?

[thatbudakguy]

Broke off the changes that add the new variants so that this PR is only the changes to the existing dark variants for easier review.

[github-actions]

A preview of this branch is available at https://sul-dlss.github.io/component-library/preview-95.

[dnoneill]

The opening of the mobile menu is kind of choppy

[thatbudakguy]

It's supposed to just be immediate (no animation at all). Is that what you see?

[dnoneill]

Yeah, currently there is animation: https://sul-dlss.github.io/component-library/header/

[thatbudakguy]

Right. This PR turns it off:

component-library/styles/header.css

Lines 62 to 67 in 6f8e490

	/* HRs in the navbar have to be positioned vertically relative to the nav lists,
	* but horizontally relative to the entire container. They aren't valid as
	* children of a <ul>, so they have to be siblings, and they can't be inside
	* an <li> because they would be counted as items in the list. Repositioning of
	* other elements during opening of the menu makes them jump around, so we also
	* have to disable animation of opening/closing the nav. */