Support binary metric

[frederikziebell]

For binary data, it would be helpful to support the binary metric as implemented in dist(metric="binary"). Currently, the only way is to pass the dist object directly, which is very memory inefficient.

[jlmelville]

The description in the doc for ?dist seems to be indicate that method = "binary" is the Jaccard/Tanimoto distance. Supporting this will require an alternative to Annoy, so it won't be happening any time soon, unfortunately.

[jlmelville]

Although not as convenient as full integration with uwot, rnndescent supports the Jaccard/Tanimoto coefficient with binary data. See the rnndescent article for details on using it with uwot.