Use Semantic HTMLements

[calebmeyer]

Summary

In the (brand new) search.js, we're disabling the default behavior of anchor tags so that the page won't try to visit their hrefs. It would be better to use a more semantic element, like a <button>.

Motivation

This is one of the lints added by the ESlint react (JSX) accessibility package. If you add an onClick handler to an anchor tag, it recommends a button instead: https://github.com/evcohen/eslint-plugin-jsx-a11y/blob/HEAD/docs/rules/anchor-is-valid.md

Describe alternatives you've considered

This is a minor accessibility win at best, so a valid alternative is to leave the code as is.

Additional context

This was requested by #541, in this comment.