Implement filter and state query url

I read `helperFn` as "Helper Function", but reading on it turns out this is not a function at all, but an object with some properties on it. The contained values represent the document+language context to load phrases from, so I would call it something related to that.

Note: The comment I put about this was just to remind myself to do that when I make that change later, so you could have left it as it was for now.