useYarn misstated in tutorial

[parkerault]

Hey, excellent tutorial! I scoured the googles and this is the only one I found that covers everything I needed.

In the README it says to add const useYarn=true to build.js and start.js. In the repo build.js doesn't have this statement. start.js has useYarn: true in the createCompiler arguments. Is this a typo or is build.js supposed to have this?

I know it would probably require starting from scratch, but ideally the repo's commit history would mirror the steps in the tutorial so people can use the diffs as a reference if they run into problems.