fix: add files list to the package

Author: bahmutov

package.json

@@ -3,6 +3,10 @@
   "version": "0.0.0-development",
   "description": "This is an example app used to showcase Cypress.io testing. For a full reference of our documentation, go to docs.cypress.io",
   "main": "index.js",
+  "files": [
+    "app",
+    "cypress"
+  ],
   "scripts": {
     "build": "npm run lint && npm run types && npm run stop-only",
     "start": "http-server app -c-1",