Add package.json with npm requirements

Author: davidsneighbour

.gitignore

@@ -1,2 +1,3 @@
 docuapi
 public/
+node_modules

README.md

@@ -15,7 +15,7 @@
 **Note:** this theme requires Hugo >= 0.56.0 to run. If you want to edit the SCSS styles, you need:
 
 * The extended Hugo version.
-* PostCSS CLI: npm install -g postcss-cli (TODO(bep) add a package.json)
+* PostCSS CLI (run `npn install` to install requirements)
 
 See the [exampleSite](https://github.com/bep/docuapi/tree/master/exampleSite) and more specific its site [configuration](https://github.com/bep/docuapi/blob/master/exampleSite/config.toml) for the available options.