lucidchart.com is a popular diagram and prototype tool.
With this integration, we could add architecture diagrams, uses cases, classes, wireframes, and much more. Specially wireframes we need to visualize and interact with it. I think it doesn't need special requirements because we can share an embedded link in lucidchart.
Export the diagram to image and attach has the disadvantage of out of sync updates and edits.
This is a example of lucidchart embbedded share:
<div style="width: 640px; height: 480px; margin: 10px; position: relative;"><iframe allowfullscreen frameborder="0" style="width:640px; height:480px" src="https://www.lucidchart.com/documents/embeddedchart/xxxx-xxx-xxxx-xxxxxx-xxxxxxx" id="jDx98dKQp2fx"></iframe></div>
The link is always the same.