Release to Maven Central

[wolfs]

Bintray is shutting down and not accepting new artifacts on March 31st. Native platform has previously been published to JCenter via Bintray.

The 0.22 milestones have been published to repo.gradle.org.

For going forward, we should probably publish the next 0.22 milestone (or final) to Maven Central. Moreover, we should probably migrate the old native platform releases to Maven Central so they stay available.

[lptr]

I've closed all 0.22 related issues, or moved them out of the milestone. The only remaining one is this:

• Remove file-events subproject #341

We should be able to merge it soon, and then we can do a 0.22 release to Maven Central.