KDL query implementation

[Patitotective]

I'm trying to implement the KDL query language (for my kdl-nim) but it's hard to create it from scratch because I've never implemented a query language before and I wanted to know if there was any already existing implementation of the KDL query language, if so please let me know, thanks.

[larsgw]

I implemented it in kdljs, though I think the spec might have changed since then (like removing the mapping syntax). I also never put it in the readme apparently, oops.

Edit: I didn't add support for sibling selectors so that might mean the structure of this implementation is unoptimal, but I hope it still helps.

[Patitotective]

Thank you.

[Patitotective]

It would also be cool if KQL had a grammar in QUERY-SPEC.md, like SPEC.md.