Contributing guidelines

[natecox]

I came across a situation yesterday where I needed a webpack asset as a part of a Django Form's Media class, and opted to write a solution based on Django Pipeline's Media mixin, which looks like:

class MyForm(forms.Form):
    ...

    class Media(WebpackBundleMedia):
        js_bundles = ["myWebpackBundle"]
        css_bundles = {"all": ["myWebpackBundle"]}

I'd like to contribute this as a contrib package, but I can't find any guidelines for contributing--which I may just be looking past. I'd appreciate it if you could fill me in on which branch I should be issuing a PR against, testing standards you expect, etc. Or, you know, if you're interested in the first place.

Thanks!