fix(demo): adjust node fill for demo

Author: bkrem

demo/src/App.css

@@ -88,14 +88,8 @@
 }
 
 /* Custom node classes */
-.my-root-node {
-  fill: red;
-}
-.my-branch-node {
-  fill: yellow
-}
-.my-leaf-node {
-  fill: green;
+.demo-node > circle {
+  fill: #2d3748;
 }
 
 /* Custom path classes */

demo/src/App.js

@@ -570,6 +570,8 @@ class App extends Component {
                     ? rd3tProps => this.state.renderCustomNodeElement(rd3tProps, this.state)
                     : undefined
                 }
+                rootNodeClassName="demo-node"
+                branchNodeClassName="demo-node"
                 orientation={this.state.orientation}
                 translate={{ x: this.state.translateX, y: this.state.translateY }}
                 pathFunc={this.state.pathFunc}