AG-420 Improve React implementation

src/groupedRowInnerRendererExample/MedalRenderer.jsx

@@ -0,0 +1,18 @@
+import React, {Component} from "react";
+
+export default class MedalRenderer extends Component {
+    constructor(props) {
+        super(props);
+
+        this.country = this.props.node.key;
+        this.gold = this.props.data.gold;
+        this.silver = this.props.data.silver;
+        this.bronze = this.props.data.bronze;
+    }
+
+    render() {
+        return (
+            <span>{this.country} Gold: {this.gold}, Silver: {this.silver}, Bronze: {this.bronze}</span>
+        );
+    }
+};