Update README.md with "maintained by community" badge

Author: gvwilson

README.md

@@ -9,6 +9,12 @@
 [![CircleCI](https://circleci.com/gh/plotly/angular-plotly.js.svg?style=svg)](https://circleci.com/gh/plotly/angular-plotly.js)
 [![Coverage Status](https://coveralls.io/repos/github/plotly/angular-plotly.js/badge.svg?branch=master&i=1)](https://coveralls.io/github/plotly/angular-plotly.js?branch=master&i=1)
 
+<div align="center">
+  <a href="https://dash.plotly.com/project-maintenance">
+    <img src="https://dash.plotly.com/assets/images/maintained-by-community.png" width="600px" alt="Maintained by the Plotly Community">
+  </a>
+</div>
+
 ---
 
 Supports Angular 9.x and up. If you want to use with Angular 8.x, please use version [`[email protected]`](https://github.com/plotly/angular-plotly.js/tree/1.x).