Update RSS FILTER library item to be more generic

Thanks for addressing this issue: https://github.com/quixio/quix-library/issues/362

This one is related - can the filter template be updated so that it isn't looking for tags  specifically? Can I have it so that I can define my own fields and values to look for?

(I think the rolling window library item does something similar, where I can define the name of the parameter I want)