Document first-load tracking in the `find` mixin
Document first-load tracking in the `find` mixin

The `have<Resources>BeenRequestedOnce` and `have<ResourcesLoadedOnce` allow tracking if the first query has completed or not.  This allows you to set a watcher on either and perform some logic when it toggles to `true`.

feathers-plus/feathers-vuex,feathers-plus/feathers-vuex