Stick stimulus version to 1.1.1 in demo

Author: guillaumebriday

index.html

@@ -6,7 +6,7 @@
     <link href="https://unpkg.com/tailwindcss@^1.0/dist/tailwind.min.css" rel="stylesheet" />
     <title>Stimulus Rails Nested Form</title>
     <script type="module" src="./src/index.js" defer></script>
-    <script src="https://unpkg.com/stimulus/dist/stimulus.umd.js" defer></script>
+    <script src="https://unpkg.com/stimulus@1.1.1/dist/stimulus.umd.js" defer></script>
 
     <script type="module" defer>
       import NestedForm from './src/index.js'