Make an easy way to pre-generate exercise diffs

[kentcdodds]

You can make a diff of any combination of app, but the most common comparisons are between the problem and solution of each step. That's the default of the deployed versions. Every time the app is deployed, those diffs need to be computed again which means the first person to see them is having to wait for them to be generated which makes the app feel slow for them.

I would like an easy way (a script) that can pre-generate the diffs for all of these problem/solution combinations so we can run this as part of the deployment process so all the pages load really fast even for the first user after a deploy.