What's the difference between .npmignore and .gitignore? What kind of files should I ignore in each?
.gitignore lists which files & folders should be omitted from any commits to the repository. You can use this repo for templates of files/folders to in your .gitignore depending on your environment.
.npmignore works similarly to .gitignore, it is used to specify which files should be omitted when publishing the package to NPM. You can read more about it in the .npmignore docs