How to extend Project View? Follow

Hello. I'm new in plugin development. In few words my new custom plugin should be able to show every .xml file in Project View in form of tree of tags (like every .java file is "root" for "tree" of it's members - fields and methods). I download IntelliJ IDEA source (intellij-community-master) but can not find any code related to Project plugin. How I'm supposed to extend Project View in the way described above? Thank you.