message: fixing offline example link
  [skip ci]
  fixes
diff: <div id="Explanation">
  Tone.Offline renders a chunk of Tone.js code into an AudioBuffer. An offline instance of Tone.Transport is passed into the callback which can be used to schedule events. It may take a moment to render the sound.
  <br><br>
  - <a href="https://tonejs.github.io/docs/#Offline">Tone.Offline</a> docs.
  + <a href="https://tonejs.github.io/docs/#Tone.Offline">Tone.Offline</a> docs.
  </div>
  </div>
  <script>
  