Add Devcontainer for use in VSCode or Codespaces

[mdp]

• Add a .devcontainer to the project to make it easier for users to get started
  • Installs Python
  • Installs pip dependencies

This allows users to spin up a Github CodeSpace or run this directly in VSCode without having to setup a Python environment on their local machine.

This is just a proposal, feel free to close this an ignore it if you don't think it's a good addition to the project.

[mdp]

By the way, this worked great for me. I was able to get > 800 titles backed up on my machine. I really appreciate the work you've put into this project. Thanks!

[yihong0618]

@mdp thanks merging it