Support parallel builds

[vy]

When log4j-changelog-maven-plugin is used with a concurrency >1, Maven displays the following warning:

[WARNING] *****************************************************************
[WARNING] * Your build is requesting parallel execution, but this         *
[WARNING] * project contains the following plugin(s) that have goals not  *
[WARNING] * marked as thread-safe to support parallel execution.          *
[WARNING] * While this /may/ work fine, please look for plugin updates    *
[WARNING] * and/or request plugins be made thread-safe.                   *
[WARNING] * If reporting an issue, report it against the plugin in        *
[WARNING] * question, not against Apache Maven.                           *
[WARNING] *****************************************************************
[WARNING] The following plugins are not marked as thread-safe in Apache Log4j Kotlin API Parent:
[WARNING]   org.apache.logging.log4j:log4j-changelog-maven-plugin:0.4.0
[WARNING] 
[WARNING] Enable debug to see precisely which goals are not marked as thread-safe.
[WARNING] *****************************************************************

[vy]

Fixed in 7c8ec0d.