JCenter will be shut down soon, migrate to Maven Cenral

[szpak]

This project seems to use JCenter to kept the binary artifacts. However, JCenter is shuting down rather soon (1st May 2021), so it would be good to migrate releasing to Maven Central (and possibly synchronize old releases with it).

For sample project configuration see:
https://github.com/rwinch/gradle-publish-ossrh-sample

And for sync of the old versions:
https://www.jfrog.com/confluence/display/BT/Syncing+with+Third-Party+Platforms