title: `ReferenceError: TextEncoder is not defined` when running `react-scripts test --env=jsdom`
body: <p>I'm using a TensorFlow encoder in my application. It works fine in my browser when the application is running but I get issues when testing that it builds:</p>
  
  <pre><code>$ npx react-scripts test --env=jsdom
  FAIL  src/App.test.js
    ● Test suite failed to run
  
      ReferenceError: TextEncoder is not defined
  
        16 | import TextField from '@material-ui/core/TextField';
        17 | import Typography from '@material-ui/core/Typography';
      &gt; 18 | import * as mobilenet from '@tensorflow-models/mobilenet';
           | ^
        19 | import * as UniversalSentenceEncoder from '@tensorflow-models/universal-sentence-encoder';
        20 | import * as tf from '@tensorflow/tfjs';
        21 | import axios from 'axios';
  
        at new PlatformBrowser (node_modules/@tensorflow/tfjs-core/src/platforms/platform_browser.ts:26:28)
        at Object.&lt;anonymous&gt; (node_modules/@tensorflow/tfjs-core/src/platforms/platform_browser.ts:50:30)
        at Object.&lt;anonymous&gt; (node_modules/@tensorflow/tfjs-core/src/index.ts:29:1)
        at Object.&lt;anonymous&gt; (node_modules/@tensorflow/tfjs-converter/src/executor/graph_model.ts:18:1)
        at Object.&lt;anonymous&gt; (node_modules/@tensorflow/tfjs-converter/src/index.ts:17:1)
        at Object.&lt;anonymous&gt; (node_modules/@tensorflow-models/mobilenet/dist/index.js:38:14)
        at Object.&lt;anonymous&gt; (src/components/model.js:18:1)
        at Object.&lt;anonymous&gt; (src/App.js:8:1)
        at Object.&lt;anonymous&gt; (src/App.test.js:3:1)
  </code></pre>
  
  <p>I'd like to get rid of that error. I've tried using the 'text-encoding' package but I'm not sure how get TextEncoder properly defined before the import happens.</p>
  
  <p>Maybe I can set a different option for <code>--env</code>?</p>
  
  <p>I get the same error without <code>--env=jsdom</code>. I believe I added it after getting similar types of not defined errors and it corrected an issue.</p>
  
  <p>Here is my test:</p>
  
  <pre><code>import React from 'react';
  import ReactDOM from 'react-dom';
  import App from './App';
  
  it('renders without crashing', () =&gt; {
    const div = document.createElement('div');
    ReactDOM.render(&lt;App /&gt;, div);
    ReactDOM.unmountComponentAtNode(div);
  });
  </code></pre>
  
  <p>So setting <code>--env=node</code> does not work either because: <code>ReferenceError: document is not defined</code>.</p>