[Accessibility] After resizing page to 320*256 focus moving to the hidden elements while navigating with the tab key.

[enstyled]

As described in https://github.com/github/accessibility-audits/issues/5262

Users with low vision who find it difficult to read the text in small font uses enlarged text with re-size, will be impacted as at 400% zoom and users will be confused if the focus move to hidden element while using keyboard tab key.

[simurai]

As a quick fix for Universe, this PR makes the title a bit smaller below 390px viewport width:

Before	After

But it's a pretty custom fix.

[rezrah]

Related to https://github.com/primer/brand/issues/514

[rfearing]

@rezrah I played around with this in Storybook and I believe this can be closed now 🎉