[chapter 3] Library issues about saas

[klyburke]

@michaelklem Thanks for noting.

1. Throughout the book, we do not give explicit instructions to add new packages. For each chapter, we put all necessary packages in the "begin" codebase. We instruct readers to start with the "begin" codebase and run yarn to install all necessary packages for the chapter. You could compare the "begin" codebases from one chapter to the next to see which new packages you need to install, if you want to continue building from your 1-begin codebase.

2. Good catch! That is a typo in the book text. In the chapter 3 codebases, we have "ts-node": "^10.8.1" in our package.json files. That version of ts-node (as well as 10.9.1 as you demonstrated) works. But if you try to run the 3-end codebase with "ts-node": "^9.1.1" - you are right, the code does not compile. I will fix that typo in the book text.