Use .js extension in example for consistency

example/lib/index.js

@@ -0,0 +1,12 @@
+var React = require("react");
+// In normal usage of the module:
+//var MatrixReactSdk = require("matrix-react-sdk");
+// Or to import the source directly from the file system:
+// (This is useful for debugging the SDK as ut seems source
+// maps cannot pass through two stages).
+var MatrixReactSdk = require("../../src/index");
+
+React.render(
+    <MatrixReactSdk.MatrixChat />,
+    document.getElementById('matrixchat')
+);