Consider the appearance of components when CSS is not loaded

[andymantell]

Bug Report

What is the issue?

When viewing an nhsuk-frontend based site without CSS there are some aspects that become very large (the back arrow) or fail to convey their purpose (the NHS logo). This doesn't matter most of the time - but this morning the CSS was failing to load on one of the covid related services in production. The service still worked (Hooray for progressive enhancement!) but the NHS logo and the back arrow marred what was otherwise still quite a usable service.

We should investigate ways to make these (and any of the other components) more usable without CSS in case this happens again. Off the top of my head - putting some fallback colours natively into the NHS SVG, and giving it and the back button SVG some inherent dimensions would be a good start.

Examples

Design system homepage without CSS:

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And one of the covid service whilst it had partial CSS

(For some reason it wasn't all missing, but the bug still rears it's head)