npm Guide: Add an opinionated style guide

[gerardo-rodriguez]

I like the idea of having an ~NPM~ npm style guide. I am inspired by this guide: https://github.com/voorhoede/npm-style-guide

~(Also, is it "npm" or "NPM" when writing it in a sentence?)~ I guess it's "npm". 🙂

[spaceninja]

I just looked this up for my blog post — It's always lowercase "npm", even in grammatically incorrect situations like the start of a sentence. 😬

Oh, and +1 for the styleguide