Add Search Box to Topics Filter on Browse Bills

## Problem

Unlike all our other search filters on the Browse Bills page, there is no search box above the "Topics" filter to help users quickly find the option they want to filter on.

To improve the bill search experience for users, we should add a search box above the "Topics" filter on the Browse Bills page (similar to the search boxes above the other filters) that allows users to type in their desired option to narrow down the list of filters and make them easier to navigate.

Current Behavior (no search box above topics):

Desired Behavior (search box above topics):

## Success Criteria
- [ ] New Search Box above the Topics filter refinement on the Browse Bills page
- [ ] This should allow users to type in a search term and then filter down the list of available topics to only those which match the term
- [ ] If possible, this should match both topics and subtopics
- [ ] If not, it's acceptable to just match on subtopics (since those are the most directly relevant)
- [ ] The box should be present in both the Desktop and Mobile view search sidebars