Add ReadTheDocs badge

Author: hinerm

README.md

@@ -2,6 +2,7 @@
 
 [![Image.sc Forum](https://img.shields.io/badge/dynamic/json.svg?label=forum&url=https%3A%2F%2Fforum.image.sc%2Ftags%2Fpyimagej.json&query=%24.topic_list.tags.0.topic_count&colorB=brightgreen&suffix=%20topics&logo=data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAA4AAAAOCAYAAAAfSC3RAAABPklEQVR42m3SyyqFURTA8Y2BER0TDyExZ+aSPIKUlPIITFzKeQWXwhBlQrmFgUzMMFLKZeguBu5y+//17dP3nc5vuPdee6299gohUYYaDGOyyACq4JmQVoFujOMR77hNfOAGM+hBOQqB9TjHD36xhAa04RCuuXeKOvwHVWIKL9jCK2bRiV284QgL8MwEjAneeo9VNOEaBhzALGtoRy02cIcWhE34jj5YxgW+E5Z4iTPkMYpPLCNY3hdOYEfNbKYdmNngZ1jyEzw7h7AIb3fRTQ95OAZ6yQpGYHMMtOTgouktYwxuXsHgWLLl+4x++Kx1FJrjLTagA77bTPvYgw1rRqY56e+w7GNYsqX6JfPwi7aR+Y5SA+BXtKIRfkfJAYgj14tpOF6+I46c4/cAM3UhM3JxyKsxiOIhH0IO6SH/A1Kb1WBeUjbkAAAAAElFTkSuQmCC)](https://forum.image.sc/tag/pyimagej)
 [![Build Status](https://github.com/imagej/pyimagej/actions/workflows/build.yml/badge.svg?branch=main)](https://github.com/imagej/pyimagej/actions/workflows/build.yml)
+[![Read the Docs](https://readthedocs.org/projects/pyimagej/badge/?version=latest)](https://pyimagej.readthedocs.io/en/latest/?badge=latest)
 [![Binder](https://mybinder.org/badge_logo.svg)](https://mybinder.org/v2/gh/imagej/pyimagej/HEAD?urlpath=%2Fdoc%2Ftree%2Fdoc)
 
 PyImageJ provides a set of wrapper functions for integration between [ImageJ2]