prevent users from using npm

Author: h-takeyeah

typing-app/.npmrc

@@ -0,0 +1 @@
+engine-strict=true

typing-app/package.json

@@ -40,5 +40,8 @@
   },
   "repository": "https://github.com/su-its/typing",
   "author": "su-its",
-  "packageManager": "[email protected]"
+  "packageManager": "[email protected]",
+  "engines": {
+    "npm": "use yarn instead"
+  }
 }