Dockerfile missing?

It seems after `v0.16x.x` `Dockerfile`s are no longer included in the `.devcontainer` directory when using vscode's "Add devcontainer configuration files".
These are critical for installing extra packages and customizing the development environment.

Is there some new functionality that deprecates this way of working with devcontainers?

```
.
├── .devcontainer
│ └── devcontainer.json
| <-- Dockerfile used to be here
├── package.json
└── src
└── index.js
```