Make it runable with docker

[WeslieDE]

Add Dockerfile and Entrypoint script to get it running as a Docker image. Allows to specify the configuration parameter as Env parameter. As an example:

docker run -e DISCORD_BOT_TOKEN=... -e DISCORD_CLIENT_ID=...

[jakobdylanc]

Thanks for the pull request! It seems a lot of people want Docker support which makes sense.

For some reason I hesitate though, and I think it's because it feels like there's a million different ways to do it. I already received another pull request for Docker support and their Dockerfile and other changes looked completely different than yours.

And then there's things like, if you're running llmcord.py in a Docker container and a local API server outside of it, they need to be able to communicate. I think this requires setting LOCAL_SERVER_URL differently which is something else I need to understand more and test myself. I don’t want to support a bunch of confused first-time Docker users who can’t get it working :)

It would also be nice if the required Python packages were automatically updated every time you run the Docker container, since litellm releases updates super often lately.

So in order for me to feel comfortable adding this I need to be confident that I'm doing it the best way possible. Maybe I’m overthinking it since I don’t know enough about Docker. In the end I just need to sit down and test with it so I can figure things out for myself.