Added alias that only list top level modules

Credits to our mighty Evan You (creator of Vue.js) @yyx990803

https://gist.github.com/yyx990803/6045243

aliases/available/npm.aliases.bash

@@ -20,3 +20,5 @@ alias nud='npm update'
 alias nr='npm run'
 alias nls='npm list'
 alias nlsg='npm list --global'
+alias ng="npm list -g --depth=0 2>/dev/null"
+alias nl="npm list --depth=0 2>/dev/null"