Extension descriptor, stored in <code>META-INF/maven/extension.xml</code> in an extension's jar artifact to
    precisely control parts of the extension and dependencies to expose in the API class loader.
    Maven uses Plexus Classworlds to build the class loader hierarchy, therefore some concepts used in this extensions
    stem from Plexus Classworlds originally.

        <field xml.attribute="true" xml.tagName="root">
          <name>root</name>
          <version>4.1.0+</version>
          <description>
            Indicates that this project is the root project, located in the upper directory of the source tree.
            This is the directory which may contain the .mvn directory.

            @since Maven 4.0.0
          </description>
          <type>boolean</type>