Enable keyword searching

[melynnduh]

This one is open for discussion on how best to implement:

PFPC would like there to be a way for users to search for certain criteria/keywords that may not correspond to something in the dataset. For example, if someone searches "free food" then we should show only food pantries and summer food sites. If someone searches "produce" we should only show places with produce.

Not sure if this will entail us trying to guess every combination of search terms someone might use? Maybe we can add some tags or keywords to the food sites, like "free", "families", "produce"?