VS Code IntelliSense enabled when developing inside a Docker container

VS Code has recently launched its Visual Studio Code Remote - Containers extension:

The Visual Studio Code Remote - Containers extension lets you use a Docker container as a full-featured development environment. It allows you to open any folder inside (or mounted into) a container and take advantage of Visual Studio Code's full feature set.

But most importantly for your use case:

This lets VS Code provide a local-quality development experience — including full IntelliSense (completions), code navigation, and debugging — regardless of where your tools (or code) are located.

I made a screencast that shows that:

1. The project is mounted inside a Docker container via VS Code itself
2. An npm package ramda.js is installed from the running container
3. VS Code IntelliSense is able to make suggestions even though the package was installed in the container.

Here's the relevant configuration file .devcontainer.json at the root of the project:

{
  "name": "My Project",
  "image": "node:12-alpine"
}