Setup the repository

[gvegayon]

1. Create a devcontainer environment for VS code, and call it "ABM benchmark".
2. Create a CI that builds the image under .devcontainer/Containerfile and uploads it to ghcr.io of this repository.
3. Create a template GitHub issue for adding new examples.
4. Create a README.md file. Let's also add a section about how to contribute to the repo, which should be along the following: "Create an issue proposing the new example...". The readme should also mention that the project contains a devcontainer environment.

Recall that this repository targets scientists in the area of epidemiology and public health, economists, and other developers working in public health.