Add searchbox

[Gozala]

Add a searchbox so we could explore tags or arbitrary input

[Gozala]

I think we should probably convert current ui slightly so that search bar is always there, but alternates own input based on user actions e.g:

• Hovering a link -> siblinks:${link.href}
• Hovering a compass -> backlinks:${document.URL}
• Hovering a selection -> similar:${getSelection().toString()}
• Clicking a tag -> tag:${tag.name}
• Clicking a keyword -> keyword:${keyword}