* added lanes to preview and compile docc docs
* added package dependency on swift-docc-plugin
* ignored all Package.resolved files
* added env variable so that the package doesn't unnecessarily pull in the docC plugin for our customers
* fix linting
* moved docC catalog for spm plugin compatibility, added empty swift file, updated Package.swift so it only builds from sources
* fixed a couple of outdated paths
* added comment to empty file
