feat: search box

[david-christiansen]

Adds a search box that uses Verso's internal metadata for a live index.

[david-christiansen]

Requries leanprover/verso#267, but the search code is by @jakobvase

[ashandoak]

@jakobvase the live search results seem to be vertically misaligned. Looks like the term (on the left) is top justified, while the category (on the right) is bottom justified within the flex container.

[jakobvase]

@jakobvase the live search results seem to be vertically misaligned. Looks like the term (on the left) is top justified, while the category (on the right) is bottom justified within the flex container.

Yeah that's how I wanted it to work. If you view it on mobile or a smaller screen, or if the term is long, the category is displayed below the term.

But you're right that on your screenshot it looks off. I'll see if I can improve that.