feat: extend sink map to handle sink factory method

[tpluscode]

Extends the sink map to accept a Sink instance as well a lazy factory method so that dynamic importing is possible

// this is a breaking change, as the export is now an ES module
// in node would be
// const { SinkMap } = require('@rdfjs/sink-map')
import { SinkMap } from '@rdfjs/sink-map'

const parsers = new SinkMap()

parsers.set('application/ld+json', async () => {
  const JsonLdParser = await import('@rdfjs/parser-jsonld')
  return new JsonLdParser()
})

Above is how I populate the map in @rdfjs/formats-common

The parser module will only be loaded when sink.import('application/ld+json', stream) for the first time