Update NPM package files list

package.json

@@ -5,5 +5,9 @@
   "author": "Mattia Roccoberton <mat@blocknot.es>",
   "license": "MIT",
   "homepage": "https://github.com/blocknotes/activeadmin_quill_editor",
-  "main": "index.js"
+  "main": "index.js",
+  "files": [
+    "app/**/*",
+    "index.js"
+  ]
 }