Extract icon information from resource uri representing tree item

[sandy081]

From @bpasero here

In my case I am showing files in the same way the explorer does. I would like to reuse the same icons the explorer uses for files without me having to introduce new icons. for that, maybe the API should allow a TreeItem to have a resource URI that we then simply take as ResourceLabel and support icons with? Even more, if we had an associated resource, we could automatically open a document with that resource on click?

[sandy081]

To verify:

• Develop an extension contributing a custom tree view where each node is a file resource. You can use resourceUri property to associate a resource to TreeItem. For example refer to FTP Explorer example.

• Verify that icons are extracted from File icon theme in VS Code.