README

<extension point="org.eclipse.wst.sse.ui.editorConfiguration">
  <sourceViewerConfiguration	
     class="org.eclipse.wst.xml.ui.StructuredTextViewerConfigurationXML"
     target="org.eclipse.core.runtime.xml, org.eclipse.wst.xml.core.xmlsource" />
  <contentOutlineConfiguration
     class="org.eclipse.wst.xml.ui.views.contentoutline.XMLContentOutlineConfiguration"
     target="org.eclipse.core.runtime.xml, org.eclipse.wst.xml.core.xmlsource" />
  <quickOutlineConfiguration
     class="org.eclipse.wst.xml.ui.internal.quickoutline.XMLQuickOutlineConfiguration"
     target="org.eclipse.core.runtime.xml, org.eclipse.wst.xml.core.xmlsource" />
</extension>

What?
http://www.eclipse.org/webtools/wst/components/sse/designs/EditorConfiguration.html
Example
http://dev.eclipse.org/viewcvs/index.cgi/sourceediting/plugins/org.eclipse.wst.jsdt.web.ui/plugin.xml?view=markup&revision=1.37&root=WebTools_Project