Adding devcontainer

[turnmanh]

fixes #61

A devcontainer allows for a faster and more smooth development experience. Also, it allows us to provide the training's contents via GitHub codespaces. To do so, the base image has to support all required packages and the data has to be pulled upon creation of the dev environment.

A prebuild speeds up the creation of a codespace by prebuilding the env. on a defined basis. Here, on every push. Alternatives, scheduled, manually etc. Also, the prebuild is made available only in Europe. Outside of Europe, the users might have to wait a couple of minutes until the codespace has spun up.

• [x] devcontainer
• [x] pre-installing pkgs.
• [x] pulling data
• [x] Include formatting of notebooks, i.e. aai colors
• [ ] support major platforms, e.g. via emulating
• [x] Add prebuild for Codespaces to speed-up the initialization
• [x] Adapt README

How to test

Open the repo on the current branch and select to open it in a codespace. The codespace shall

• spin up quickly
• provide all files from the training
• provide all the data required in ./data
• provide the req. python env. s.t. the notebooks can be executed directly in the codespace

[turnmanh]

@fariedabuzaid, I am having issues to install the cvxopt pkg. in a linux/arm64 image. For now, I'll not provide a solution for different architectures but will keep this for the future. This is fine, as the devcontainer is mainly intended to support codespaces, which it does.

[turnmanh]

To test the feature, feel free to open a Codespace on the branch adding-devcontainer and step through the notebooks.