Add docker

[tharvik]

When trying out rust-stainless, I found it hard to setup. So I built a docker image out of the instruction, that will probably help new users using it before really installing it.

• from a debian image as it needs both rust and java (and alpine uses musl with isn't working with some deps)
• add a CI pass to build it
• lock some deps version
  • it seems that your main branch fails to build currently
  • some deps doesn't work with choosen toolchain

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