add alternative package to readme (django-webpack#247)

add alternative package to readme

Author: Elliot Charney

README.md

@@ -413,3 +413,9 @@ Then in your base jinja template:
 
 
 Enjoy your webpack with django :)
+
+# Alternatives to Django-Webpack-Loader
+
+_Below are known projects that attempt to solve the same problem:_
+
+* [Django Manifest Loader](https://github.com/shonin/django-manifest-loader)