docs: added a section for usage with process.env (#14)

added a header for usage with process.env to separate section from 'current lifecycle event' and make it easier to find

PR-URL: #14
Credit: @mwarger
Reviewed-By: @zkat

doc/misc/npm-scripts.md

@@ -143,7 +143,9 @@ The package.json fields are tacked onto the `npm_package_` prefix. So,
 for instance, if you had `{"name":"foo", "version":"1.2.5"}` in your
 package.json file, then your package scripts would have the
 `npm_package_name` environment variable set to "foo", and the
-`npm_package_version` set to "1.2.5"
+`npm_package_version` set to "1.2.5".  You can access these variables 
+in your code with `process.env.npm_package_name` and 
+`process.env.npm_package_version`, and so on for other fields.
 
 ### configuration