settings.html

<div id="markdown-settings-panel">
    <div class="md-settings-row">
        <span class="md-settings-label">Format</span>
        <select id="markdown-preview-format">
            <option>Standard Markdown</option>
            <option>GitHub-Flavored (GFM)</option>
        </select>
    </div>
    <div class="md-settings-row">
        <span class="md-settings-label">Theme</span>
        <select id="markdown-preview-theme">
            <option value="clean">Light</option>
            <option value="dark">Dark</option>
            <option value="serif">Classic</option>
            <option value="github">GitHub</option>
            <option value="custom">Custom</option>
        </select>
    </div>
    <div>
        <span class="md-settings-label"></span>
        <label><input type="checkbox" id="markdown-preview-sync-scroll">Sync scroll position</label>
    </div>
</div>