Support loading JSON-LD into `RDFStore`

[multimeric]

As far as I can tell, it only supports loading TTL:

prez-ui/packages/prez-lib/src/store.ts

Lines 35 to 40 in d108095

	/**
	* Parses an RDF string in Turtle format into a store
	*
	* @param s RDF Turtle string
	*/
	public load(s: string) {