Added a module type declaration.

Author: eyuell21

implement-shell-tools/cat/package.json

@@ -3,6 +3,7 @@
   "version": "1.0.0",
   "description": "You should already be familiar with the `cat` command line tool.",
   "main": "cat.js",
+  "type": "module",
   "scripts": {
     "test": "echo \"Error: no test specified\" && exit 1"
   },