chore(docs): Fix left nav menu and restore di to nav

I'm trying to figure out how to get di.dart back in the left nav. I thought --include-dependent-packages would have done that, but it doesn't seem to work unless I explicitly create a module under lib/ that has the export 'package:di/di.dart' statement in it.  This PR also drops the top-level "angular" from the left-nav to eliminate duplication in the docs.