yaml/resources/intellij.graphql.yaml.xml

<idea-plugin package="com.intellij.graphql.yaml">
  <dependencies>
    <plugin id="org.jetbrains.plugins.yaml"/>
  </dependencies>

  <extensions defaultExtensionNs="com.intellij">
    <codeInsight.lineMarkerProvider language="yaml"
                                    implementationClass="com.intellij.graphql.yaml.GraphQLIntrospectionYamlLineMarkerProvider"/>
  </extensions>
</idea-plugin>