Add Docker instructions

[jouir]

I'm running Chia on Docker using the official Chia Docker container. I wanted to integrate chiadog to my Docker environment so this commit brings a Dockerfile and instructions on how to setup chiadog using Docker.

[skweee]

Great start! I agree that it would be good to have a Dockerfile in this repo. I have a couple of improvement wishes though, which you can also find in my pull request for the repo by @ajacobson (that's the one I'm using right now, but I would gladly switch): https://github.com/skweee/chiadog-docker/blob/feature/add-branch-argument/Dockerfile

• Please also make the repository configurable to support builds from forks while making the default the original repo.
• To minimize the image size, you only need to make a shallow clone of the repo ("git clone --depth 1 [...]").
• I would be great if you could make the time zone configurable (e.g. using the TZ env variable as in the example above - also note the entrypoint.sh). Otherwise people will have to set the time of day for their daily stats using UTC.

Thanks for the contribution!

[jouir]

I didn't know there was a chiadog-docker repository doing exactly what I was looking for. No need to re-invent the wheel, I'm closing this pull-request. Thanks for sharing!