use javadoc.io for javadoc hosting?

[maxcellent]

Not sure how javadoc is managed currently. But I hope this could save some effort on every release.

Basically https://javadoc.io/doc/com.google.errorprone/error_prone_annotation will always point to the latest version published to JCenter / Central Maven.

Or you can add a badge with versions always up to date:

[![javadoc](https://javadoc.io/badge2/com.google.errorprone/error_prone_annotation/javadoc.svg)](https://javadoc.io/doc/com.google.errorprone/error_prone_annotation)

Disclaimer: I creates javadoc.io

[tausiflife]

Can i work on this?