fix SPA mode watcher path in react-hooks template Signed-Off-By: Lorenzo Pomili <pomili.lorenzo85@gmail.com> (#4114)

Author: lorenzo-pomili

jscomp/bsb/templates/react-hooks/index.html

@@ -17,6 +17,6 @@
   <!-- This is https://github.com/marijnh/moduleserve, the secret sauce that allows us not need to bundle things during development, and have instantaneous iteration feedback, without any hot-reloading or extra build pipeline needed. -->
   <script src="/moduleserve/load.js" data-module="/src/Index.bs.js"></script>
   <!-- Our little watcher. Super clean. Check it out! -->
-  <script src="./watcher.js"></script>
+  <script src="/watcher.js"></script>
 </body>
 </html>