Example taskcluster worker

So this should be a combination of workerType and provisionerId rather then routing... Routing is primarily intended for dispatching messages to services independent of _how_ the task was run (worker only cares about how).

Examples of what routing is designed for are:

 - indexing tasks
 - treeherder

The really important bit is routing can be specified by any task (so unless your trying to show that here I would use the above suggestion)