build(dev): Fix dev server not showing mermaid.js

When moving to the mono-repo,
`<script src="http://localhost:9000/mermaid.js"/>`
stopped working, since the vite dev server was exposing
the `./dist` folder, when the folder had moved to
the `./packages/mermaid/dist` folder.

.vite/server.ts

@@ -13,7 +13,7 @@ async function createServer() {
   });
 
   app.use(vite.middlewares);
-  app.use(express.static('dist'));
+  app.use(express.static('./packages/mermaid/dist'));
   app.use(express.static('demos'));
   app.use(express.static('cypress/platform'));