Add button to clear search field

Created by: gracewashere

Closes #121 (closed).

Problem:

Users cannot clear their search unless they re-submit the search with an empty field, or click on the resource link in the navigation bar.

Solution:

Add a button for clearing out the search field and going back to showing all resources.

## To Do - [ ] Only show clear icon when there is text in the search bar - [ ] CHANGELOG