fix(project): correct library default export

index.js

@@ -1 +1,3 @@
-export default './lib/Viewer';
+export {
+  default
+} from './lib/Viewer';

test/spec/ViewerSpec.js

@@ -2,6 +2,8 @@ import TestContainer from 'mocha-test-container-support';
 
 import Diagram from 'diagram-js/lib/Diagram';
 
+import ViewerDefaultExport from '../../';
+
 import Viewer from 'lib/Viewer';
 
 import inherits from 'inherits';
@@ -980,4 +982,9 @@ describe('Viewer', function() {
 
   });
 
+
+  it('default export', function() {
+    expect(ViewerDefaultExport).to.equal(Viewer);
+  });
+
 });