fix: module import in pie chart demo

demos/pie.html

@@ -36,8 +36,8 @@
       "Iron" :  5
     </pre>
 
+    <script src="./mermaid.js"></script>
     <script type="module">
-      import mermaid from '../packages/mermaid';
       mermaid.initialize({
         theme: 'forest',
         // themeCSS: '.node rect { fill: red; }',