samples/applicationConfigurable/src/META-INF/plugin.xml

<idea-plugin version="2">
  <name>applicationConfigurable</name>
  <description>This sample plugin illustrates how to contribute to the applicationConfigurable
    extension point available in the IDEA core.
  </description>
  <version>1.0</version>
  <vendor>JetBrains</vendor>
  <!--
  <idea-version since-build="8000"/>
   -->
  <application-components>
    <!-- Add your application components here -->
  </application-components>

  <project-components>
    <!-- Add your project components here -->
  </project-components>

  <actions>
    <!-- Add your actions here -->
  </actions>

  <extensions defaultExtensionNs="com.intellij">
    <!-- Add your extensions here -->
      <applicationConfigurable implementation="fontConfigurable.MyExtensConfigurable"></applicationConfigurable>
  </extensions>
</idea-plugin>