Create 'render interactive' button

[jonocodes]

Kind of like those CI banners that show in readme's on github. Or like the 'Try in PWD' link mentioned here: docker-library/docs#912

This would effectively launch the readme in pwder.io so you dont have to know how to cut and paste it in there. Discoverability. This way someone who finds the readme can run it.

We then might want to make sure that that image does not show when rendered.