Added test of usage via webpack to the e2e tests

e2e/platform/bundle-test.js

@@ -0,0 +1,10 @@
+import mermaid from '../../dist/mermaid.core'
+
+mermaid.initialize({
+  theme: 'forest',
+  gantt: { axisFormatter: [
+    ['%Y-%m-%d', (d) => {
+      return d.getDay() === 1
+    }]
+  ] }
+})