use nexus-staging-maven-plugin for automating release process

[bitcoder]

• https://gist.github.com/sualeh/ae78dc16123899d7942bc38baba5203c
• https://help.sonatype.com/en/configuring-your-project-for-deployment.html
• https://stackoverflow.com/questions/46985231/is-nexus-staging-maven-plugin-needed-if-using-maven-release-plugin