Update README.md with "maintained by community" badge

Author: gvwilson

README.md

@@ -14,6 +14,12 @@ An R package for creating interactive web graphics via the open source
 JavaScript graphing library
 [plotly.js](https://github.com/plotly/plotly.js).
 
+<div align="center">
+  <a href="https://dash.plotly.com/project-maintenance">
+    <img src="https://dash.plotly.com/assets/images/maintained-by-community.png" width="400px" alt="Maintained by the Plotly Community">
+  </a>
+</div>
+
 ## Installation
 
 Install from CRAN: