title: monaco-editor tokenizer do not support "ignore case" regex
body: <p>The <code>tokenizer</code> in <code>monaco-editor</code> do not seem to support 'ignore case' <code>i</code> flag in regex. Sample code below,</p>
  <p>To replicate, you can paste this in <a href="https://microsoft.github.io/monaco-editor/playground.html" rel="nofollow noreferrer">playground</a> and try running yourself.</p>
  <pre><code>monaco.languages.register({ id: 'sample' });
  monaco.languages.setMonarchTokensProvider('sample', {
      tokenizer: {
          root: [
              [/cmd1|cmd2/i, 'keyword']
          ]
      }
  });
  
  monaco.editor.create(document.getElementById('container'), {
      value: &quot;cmd1 10\nCMD2 10&quot;,
      language: 'sample'
  });
  </code></pre>
  <p><code>cmd1</code> turns blue while <code>CMD2</code> do not.</p>
  <p>Is this intentional? Is there a way around?</p>