dillon1000/react

[snap tester] watch mode: ignore changes from test updates

A bit of a hack - 

We currently trigger test runs when we detect changes in the test fixtures 
directory. This trigger is also hit when we run `snap` in update mode, since 
updating performs file writes. 

This PR will ignore subscription changes (callbacks) that trigger within 5 
seconds of the last update. 

It seems difficult to be more granular with a timestamp, since `@parcel/watcher` 
doesn't give us the file change timestamp and (from my understanding), other 
promises and tasks can be queued to run between the update and callback.