Add a list of redis commands (documentation improvement)

[bastbnl]

I stumbled on this post and decided to apply the rename-command documented in step 5 - Renaming Dangerous Commands on the redis server used by the project I'm working on. This project has celery, channels_redis and django-redis, so I thought I'd take a look to see which commands could be renamed.

Looking through the celery RedisBackend, I found that this project includes a list of celery commands used by the backend and I was unable to find such a list for channels_redis, so I decided to add one in a PR. I'm not sure that this list is the complete list of commands used by the modules, but it should contain the most obvious commands