@1aura =>  add blog post around building a plugin

Hiya :sun_with_face: 
I would rephrase, something like: 
We've been trying to apply this to testing.
In order to show the results of failing (snapshot) tests in a more visual way, I've had to extend Xcode and built... OR
To that end, I've extended Xcode to show the results of failing (snapshot) tests in a more visual way by building...

maybe you should specify that these are snapshot tests. I think you could also combine this paragraph with the one above, they're both really short.