How to add a quote share button in Webflow

(function() {
  var style = document.createElement('style');
  style.textContent =
    '.share-quote-btn { position: fixed; background: #111; color: #fff; padding: 8px 14px;' +
    'border-radius: 100px; font-size: 13px; cursor: pointer; z-index: 9999; display: none;' +
    'align-items: center; gap: 6px; border: none; font-family: inherit; white-space: nowrap;' +
    'box-shadow: 0 4px 12px rgba(0,0,0,0.15); transition: opacity 0.2s; }' +
    '.share-quote-btn:hover { opacity: 0.85; }';
  document.head.appendChild(style);

  var btn = document.createElement('button');
  btn.className = 'share-quote-btn';
  btn.innerHTML = '🔗 Share this quote';
  document.body.appendChild(btn);

  var selectedText = '';

  document.addEventListener('mouseup', function(e) {
    var sel = window.getSelection();
    var text = sel ? sel.toString().trim() : '';
    if (text.length < 20) { btn.style.display = 'none'; return; }

    selectedText = text;
    btn.style.display = 'flex';
    btn.style.top = (e.pageY - 50) + 'px';
    btn.style.left = Math.min(e.pageX - 60, window.innerWidth - 220) + 'px';
  });

  document.addEventListener('mousedown', function(e) {
    if (e.target !== btn) btn.style.display = 'none';
  });

  btn.addEventListener('click', function() {
    var url = window.location.href;
    var twitterUrl = 'https://twitter.com/intent/tweet?text=' +
      encodeURIComponent('"' + selectedText.substring(0, 200) + '"') +
      '&url=' + encodeURIComponent(url);

    if (navigator.share) {
      navigator.share({ title: document.title, text: '"' + selectedText + '"', url: url });
    } else {
      window.open(twitterUrl, '_blank');
    }
    btn.style.display = 'none';
  });
})();

var linkedinUrl = 'https://www.linkedin.com/sharing/share-offsite/?url=' +
  encodeURIComponent(url) + '&summary=' + encodeURIComponent('"' + selectedText + '"');
window.open(linkedinUrl, '_blank');