Updated filter values to persist through searches

[aidenszeto]

Relevant issue

Closes #525

Summary of change

• Updated listing filter values to persist through multiple searches
• Addressed react warnings (triple equals and unused import)

Testing/Verification

• Select any filter value using the filter modal (ie. max price, country, price: low to high)
• Hit confirm and search to display filtered listings
• Click on the filter icon again. The filter modal should contain the filters that are currently applied

[aidenszeto]

The functionality of the filter values persisting works perfectly (after clicking search)! However, I do want to bring attention to the situation where the user clicks on the filter button then escapes the modal and clicks it again. The filter values don't persist, which may not be a huge deal but it's just a weird use-case scenario we might want to look into.

Also, in the ticket task, we suggested implementing a clear filters option, but that could be left for another time if that's not a huge priority.

Thanks for pointing those out, just added the clear button with latest commit. I think it might be alright to have the filter not save when the user clicks out of the modal and rather have it save only when the filter is applied. Anyone else have thoughts?