Add devcontainer.json

[matthewruzzi]

Closes #1796

[matthewruzzi]

The Node.js example dev container has a launch.json file. Should we add one?

{
    // Use IntelliSense to learn about possible attributes.
    // Hover to view descriptions of existing attributes.
    // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
    "version": "0.2.0",
    "configurations": [
        {
            "type": "node-terminal",
            "name": "Run Script: start",
            "request": "launch",
            "command": "npm run start",
            "cwd": "${workspaceFolder}"
        }
    ]
}