Fix/325 responsive breadcrumb

[adamwoodnz]

Fixes #325

Alternative to #348, which rather than truncating the central breadcrumbs, simply lets them stack, see comment.

It also updates the styles to match the Developer designs.

Screenshots

Desktop	Tablet	Mobile

[StevenDufresne]

This looks good.

We'll need to update the documentation site

Example: https://wordpress.org/documentation/article/learn-about-wordpress-and-version-history/

[jasmussen]

Looks good at a glance. The only thing we might tweak is the line-height which can get a bit compact on mobile, but we can ship this as is and revisit if need be.

[adamwoodnz]

We'll need to update the documentation site

@jasmussen what do you think about rolling out these breadcrumbs on Documentation before we undergo the full reskin?

Design

Current

It might be a sort of hybrid with the breadcrumbs moving out of the blue bar and sitting below, or we could also change that blue bar to charcoal, as is currently in progress on Developer:

[StevenDufresne]

We can make documentation look the same as the developer handbook pages since they are essentially the same thing.
Move the breadcrumb down into the content, add the title to the subnav and change the color. I would just ping #docs with that change to make sure everyone is aware.

[adamwoodnz]

I only ask because Documentation is supposed to be going through a much wider reskin, and want to check that this new navigation style is compatible.

[adamwoodnz]

The Docs update is now underway, and actually removes the breadcrumbs WordPress/wporg-documentation-2022#67

[jasmussen]

I have to offer an apology there, the breadcrumbs are meant to be there and I corrected this in the mockups.