Update README.md with "maintained by Plotly" badge

Author: gvwilson

README.md

@@ -6,6 +6,12 @@ functionality. It is a React port of the jQuery-based
 
 `react-pivottable` is part of Plotly's [React Component Suite](https://plot.ly/products/react/) for building data visualization Web apps and products.
 
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+  <a href="https://dash.plotly.com/project-maintenance">
+    <img src="https://dash.plotly.com/assets/images/maintained-by-plotly.png" width="400px" alt="Maintained by Plotly">
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 ## What does it do & where is the demo?
 
 `react-pivottable`'s function is to enable data exploration and analysis by