Bar graph added.

node_modules/vega-expression/index.js

@@ -0,0 +1,20 @@
+export {
+  RawCode,
+  Literal,
+  Property,
+  Identifier,
+  ArrayExpression,
+  BinaryExpression,
+  CallExpression,
+  ConditionalExpression,
+  LogicalExpression,
+  MemberExpression,
+  ObjectExpression,
+  UnaryExpression,
+  default as ASTNode
+} from './src/ast';
+
+export { default as parse} from './src/parser';
+export { default as codegen } from './src/codegen';
+export { default as functions } from './src/functions';
+export { default as constants } from './src/constants';