Search button overlaps logo on very small screens

[johnnymatthews]

This was raised in #214 by @david-on-github:

I am seeing a pre-existing issue it seems, but the search icon is positioned absolute and overlays at very super small screens, and everything gets a bit wonky at really smaller sizes due to the header css.
But most of this is coming from docusaurus itself, and happens on their website also. Likely more effort to fix/maintain than worth.

Fix

The likely fix is to either:

1. Start shrinking the logo at 344px.
2. Move the search icon to the hamburger menu at some other point before 344px.

Screenshots that might be useful

344px	304px (where it start shrinking the logo)