Following (Maven Guide)[https://maven.apache.org/guides/mini/guide-3rd-party-jars-local.html] it is possible to add the an external JAR as a depencie.
mvn install:install-file -Dfile=<path-to-file> -DgroupId=<group-id> -DartifactId=<artifact-id> -Dversion=<version> -Dpackaging=<packaging>
Example:
mvn install:install-file -Dfile=polymer-components-0.5.2-RELEASE.jar -DgroupId=org.webjars -DartifactId=polymer-components -Dversion=0.5.2-RELEASE -Dpackaging=jar