Merge pull request PANTHEONtech#26 from rovarga/javadoc

Add javadoc.io badge

README.md

@@ -3,6 +3,7 @@
 [![CII Best Practices](https://bestpractices.coreinfrastructure.org/projects/2172/badge)](https://bestpractices.coreinfrastructure.org/projects/2172)
 [![FOSSA Status](https://app.fossa.io/api/projects/git%2Bgithub.com%2FPantheonTechnologies%2Ftriemap.svg?type=shield)](https://app.fossa.io/projects/git%2Bgithub.com%2FPantheonTechnologies%2Ftriemap?ref=badge_shield)
 [![Maven Central](https://maven-badges.herokuapp.com/maven-central/tech.pantheon.triemap/triemap/badge.svg)](https://maven-badges.herokuapp.com/maven-central/tech.pantheon.triemap/triemap)
+[![Javadocs](https://www.javadoc.io/badge/tech.pantheon.triemap/triemap.svg)](https://www.javadoc.io/doc/tech.pantheon.triemap/triemap)
 [![License](https://img.shields.io/badge/License-Apache%202.0-blue.svg)](https://opensource.org/licenses/Apache-2.0)
 
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