Render the docs search bar on all branches

[brookslybrand]

tl;dr

Render the docs search bar on all docs (main, dev, previous versions, etc.)

Context

Recently I shared a tweet hyping up some changes coming to the next version of Remix.

This highlighted the fact that switching between branches causes the search bar to disappear.

I summarized the reason and the remediation options as follows

It's happening because we only render the search box for main branch. We only render it for main because that's the only docs we index.

So either we need to: a) index other branches b) just show the search box on every branch, even though it's only searching main

For the sake of consistency between branches, let's go with b for now. If we find that this causes confusion or frustration for users we can further enhance it with some sort of message or by implementing a