Release 0.9.3

It's probably time to do another release.  Y'all should take a look at this and double-check that the CHANGELOG is accurate and I've updated the release # in all the right places.

@paulmillr or @ljharb would need to actually do the `npm publish`; I don't have permissions for that.  You should probably push a git tag at the same time, although technically I could do that I think.