Add support for channels configuration

[fkromer]

Would be great to have support for channel layer configuration in django-environ 😏 The in-memory channel layer config is pretty simple. The channel_redis config one is more interesting.

[AstraLuma]

please, this is rapidly becoming extremely annoying.

[kevinrenskers]

That would be really nice to have. As I workaround I did it like this, but hopefully there's a better solution?

env = environ.Env(
    DEBUG=(bool, False),
    CI=(bool, False),
)

if env("CI"):
    CHANNEL_LAYERS = {
        "default": {"BACKEND": "channels.layers.InMemoryChannelLayer"},
    }
else:
    CHANNEL_LAYERS = {
        "default": {
            "BACKEND": "channels_redis.core.RedisChannelLayer",
            "CONFIG": {
                "hosts": [("127.0.0.1", 6379)],
            },
        },
    }

[sergeyklay]

Implemented in #514. Thank you for contributing.