update readable-stream to v3

[goto-bus-stop]

requires stream-browserify to be updated too.

[legobeat]

Addressed in #2070

[legobeat]

There is still a transitive runtime dependency on readable-stream@2, via read-only-stream.

Unfortunately, the author and sources are MIA from GitHub.

I see some conflicting information from the last snapshot from web.archive.org indicating a last commit of v2.0.0 (the published version of which still depends on readable-stream@2) whereas the last commit on index.js indicates "streamsv3".

The only remaining fork seems to be https://github.com/juliangruber/read-only-stream, which is missing those original and newer contributions.

On the other hand, the module is fairly small, readable, and not minified or anything so if it comes down to it, it doesn't seem untenable for someone else than substack to pick up the published version from the NPM registry and see what if anything beyond a change in package.json is needed to make it compatible with streamsv3.

@juliangruber

[ljharb]

An alternative is that I could pursue going through github and substack to get the repo revived and the npm access turned over; i've done it for a dozen of substack's packages already.