Bar graph added.

node_modules/vega-hierarchy/index.js

@@ -0,0 +1,7 @@
+export {default as nest} from './src/Nest';
+export {default as pack} from './src/Pack';
+export {default as partition} from './src/Partition';
+export {default as stratify} from './src/Stratify';
+export {default as tree} from './src/Tree';
+export {default as treelinks} from './src/TreeLinks';
+export {default as treemap} from './src/Treemap';