message: fix(devtools): prevent devTools to load when not text/html document
  On Firefox, Angular DevTools was breaking the XML display because of the script injected
  Based on contentType, we won't inject that script anymore
  Fixes
  PR Close
diff: @@ -14,7 +14,9 @@ window.addEventListener('message', (event: MessageEvent) => {
  }
  });
  +if (document.contentType === 'text/html') {
  const script = document.createElement('script');
  script.src = chrome.runtime.getURL('app/detect_angular_for_extension_icon_bundle.js');
  document.documentElement.appendChild(script);
  document.documentElement.removeChild(script);
  +}
  