vscode-extension-samples/webpack-sample/.vscode/launch.json

// A launch configuration that compiles the extension and then opens it inside a new window
{
    "version": "0.2.0",
    "configurations": [
        {
            "name": "Launch Extension",
            "type": "extensionHost",
            "request": "launch",
            "runtimeExecutable": "${execPath}",
            "args": [
                "--extensionDevelopmentPath=${workspaceFolder}"
            ],
            "outFiles": [
                "${workspaceFolder}/dist/**/*.js"
            ],
            "preLaunchTask": "npm: webpack"
        }
    ]
}