Add missing fields to the pom.xml file to publish in maven central

[stefano81]

See https://maven.apache.org/repository/guide-central-repository-upload.html

[br-arruda]

Hi Stefano, requirement 2 tells about javadocs and source, and the Maven example for it is here: https://maven.apache.org/plugin-developers/cookbook/attach-source-javadoc-artifacts.html

I made that change locally but didn't send the PR for it because I think there is something wrong with javadocs. It was my first time dealing with this. I documented a class in the project for testing but the resulting jar was missing it. I don't know what was wrong, or if it worked and there was problems with IDE as docs was incomplete.

If you give me the guidelines, I can help you on that.

[stefano81]

Hi @BrunoArruda I prepared a branch too. Have a look if you see any possible improvement.
I'll have a look at javadocs as soon as possible.