Add Washington, DC chapter to README

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README.md

@@ -16,6 +16,7 @@ Here are our official chapters. Let us know if you are interested in [starting o
 * [Boston](http://www.meetup.com/Papers-We-Love-Boston/)
 * [Singapore](https://www.facebook.com/groups/paperswelovesg/)
 * [Bangalore](http://www.meetup.com/Papers-we-love-Bangalore/)
+* [Washington, DC](http://www.meetup.com/Papers-We-Love-DC/)
 
 All of our meetups follow our [Code of Conduct](CODE_OF_CONDUCT.md).