message: Fix mistakes in options.html
  1. The input tag is self-closing
  2. The max-length attribute is counterproductive
diff: <label>
  <strong>Personal token</strong>, <a id="personal-token-link" href="https://github.com/settings/tokens/new?description=Refined%20GitHub&scopes=repo" target="_blank">found here</a> (<a href="https://github.com/sindresorhus/refined-github/search?q=libs/api" target="_blank">some features</a> use the API)<br>
  <!-- placeholder is set to enable use of :placeholder-shown CSS selector -->
  - <input type="text" name="personalToken" spellcheck="false" autocomplete="off" maxlength="40" pattern="[\da-f]{40}" placeholder=" "></input>
  + <input type="text" name="personalToken" spellcheck="false" autocomplete="off" pattern="[\da-f]{40}" placeholder=" ">
  </label>
  </p>
  