Where is react.js?

[pabrams]

When I use vss-web-extension-sdk, it seems to be able to use some older version of react.js without actually including it anywhere (never doing npm install react or including it in package.json). I can see it in my browser downloaded from somewhere under a _static/TFS folder, but how did it get on the server?

tsconfig:

{
    "compilerOptions": {
        "module": "amd",
        "moduleResolution": "node",
        "target": "es5",
        "sourceMap": false,
        "jsx": "react",
        "outDir": "dist/"
    },
    "types": ["vss-web-extension-sdk"],
    "exclude": [
        "node_modules"
    ]
}

project dependencies:

  "devDependencies": {
    "tfx-cli": "^0.6.4",
    "typescript": "^2.7.0"
  },
  "dependencies": {
    "es6-object-assign": "^1.1.0",
    "vss-web-extension-sdk": "^5.141.0"
  }

excerpt from vss-extension.json:

    "files": [
        {
            "path": "img",
            "addressable": true
        },
        {
            "path": "dist",
            "addressable": true
        },
        {
            "path": "index.html",
            "addressable": true,
            "contentType": "text/html"
        },
        {
            "path": "css",
            "addressable": true
        },
        {
            "path": "dialog.html",
            "addressable": true,
            "contentType": "text/html"
        },
        {
            "path": "node_modules/es6-object-assign/dist/object-assign-auto.min.js",
            "addressable": true
        },
        {
            "path": "node_modules/vss-web-extension-sdk/lib/VSS.SDK.min.js",
            "addressable": true
        }
    ],