title: How to add context menu with VSCode extension?
body: <p>How do you add a context menu? (in the explorer and/or the editor)</p>
  
  <p>I tried the following which doesn't work:</p>
  
  <pre><code>{
      "command": "extension.sayHello",
      "title": "Say Hello",
      "context": {
          "where": "explorer/context",
          "when": "json"
      }
  }
  </code></pre>
  
  <p>That's based on:</p>
  
  <p><a href="https://github.com/Microsoft/vscode/issues/3192" rel="noreferrer">https://github.com/Microsoft/vscode/issues/3192</a></p>
  
  <p><a href="https://github.com/Microsoft/vscode/pull/7704" rel="noreferrer">https://github.com/Microsoft/vscode/pull/7704</a></p>