Added Treeware badge and license

Author: JamesMessinger

README.md

@@ -62,6 +62,8 @@ License
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 coverage-istanbul-loader is 100% free and open-source, under the [MIT license](LICENSE). Use it however you want.
 
+This package is [Treeware](http://treeware.earth). If you use it in production, then we ask that you [**buy the world a tree**](https://plant.treeware.earth/JS-DevTools/coverage-istanbul-loader) to thank us for our work. By contributing to the Treeware forest you’ll be creating employment for local families and restoring wildlife habitats.
+
 
 
 Big Thanks To