This suggestion is in regards to page 114 in the pdf, for the chapter Deploying the Site. After the editing package.json, the following git instructions are shown:
$ git add config.toml
$ git commit -m "Set the ..."
$ git push origin master
This looks like copy pasta from the previous paragraphs on updating the config.toml and should probably be:
$ git add package.json
$ git commit -m "Set the ..."
$ git push origin master