Formula-Cookbook: add std_npm_args

Signed-off-by: Patrick Linnane <[email protected]>

docs/Formula-Cookbook.md

@@ -514,6 +514,16 @@ The `std_*_args` methods, as well as the arguments they pass, are:
 "--wrap-mode=nofallback"
 ```
 
+#### `std_npm_args`
+
+```ruby
+"require 'language/node'"
+
+"return Language::Node.std_npm_install_args(Pathname(prefix)) if prefix"
+
+"Language::Node.local_npm_install_args"
+```
+
 #### `std_pip_args`
 
 ```ruby