package-lock.json in .gitignore

Hi,

As discussed on the Workers Discord, here is an issue to discuss this.
NPM recommends `package-lock.json` to be included in commits, for reasons discussed in this SO question: https://stackoverflow.com/questions/44206782/do-i-commit-the-package-lock-json-file-created-by-npm-5

Here is the line in question:
https://github.com/cloudflare/worker-template-router/blob/72da356ea761cb0121ed9a70e402faabc5823d02/.gitignore#L4