Improve search

[xfbs]

I think we can show some more metadata in the search results to be able to more easily filter them.

Currently, we display a little square with the crate name, version and description.

My idea would be:

• add download count, number of versions, categories/tags
• add a foldout for more information (button on the bottom)

This is the crates.io UI for search results. I think it looks good. I guess one question would be: when people use diff.rs, what kind of information are they looking for? Download count is usually a good indication of whether or not you are looking at the right crate.

[xfbs]

Another idea: for searching crate contents, we could use something like the trigram crate, which allows us to do fuzzy searching.