Balsamiq Wireframes allows you to create, edit and share sketch-quality wireframes, all within Google Docs
Balsamiq Wireframes is the easiest, fastest, most fun, best supported wireframing tool on the Internet. The integration with Google Drive and G Suite is pretty slick: you can create or edit wireframes projects all within the browser. You can even collaborate on your wireframes with others, in real time!
The free Balsamiq Wireframes add-ons allow you to quickly browse and insert your wireframes in your Google Docs.