implement metadata for SPARQL queries

[egonw]

See https://github.com/JervenBolleman/wikibase-sparql-examples/blob/main/examples/wikidata/000c94654373277a9c231bd48b077313.ttl

The idea is to have this as "source" and the current SPARQL files (and folders) are created from these source files (with a GitHub Actino). @marvinm2, @DeniseSl22, if you agree, plz give a thumbs up, and I will give this a go.

cc @JervenBolleman, @andrawaag

[egonw]

During the Scholia hackathon I had a good look at Jerven's proposed format and tools around it, and just launched this two-query website: https://bigcat-um.github.io/sparql-examples/

[egonw]

Okay, moving this forward.

[egonw]

In progress. It will now pick up .ttl files and automatically convert those to matching .rq files, see e.g. https://github.com/wikipathways/SPARQLQueries/tree/master/A.%20Metadata