Caches the Yarn resolution for faster installs

Author: Maël Nison

package.json

@@ -15,7 +15,8 @@
     "screencast": "node ./tasks/screencast.js",
     "screencast:error": "svg-term --cast jyu19xGl88FQ3poMY8Hbmfw8y --out screencast-error.svg --window --at 12000 --no-cursor",
     "test": "cd packages/react-scripts && node bin/react-scripts.js test",
-    "format": "prettier --trailing-comma es5 --single-quote --write 'packages/*/*.js' 'packages/*/!(node_modules)/**/*.js'"
+    "format": "prettier --trailing-comma es5 --single-quote --write 'packages/*/*.js' 'packages/*/!(node_modules)/**/*.js'",
+    "compile:lockfile": "node tasks/compile-lockfile.js"
   },
   "devDependencies": {
     "async-sema": "^2.1.3",

packages/create-react-app/createReactApp.js

@@ -243,6 +243,14 @@ function createApp(name, verbose, version, useNpm, usePnp, template) {
       version = 'react-scripts@0.9.x';
     }
   }
+
+  if (useYarn) {
+    fs.copySync(
+      require.resolve('./yarn.lock.cached'),
+      path.join(root, 'yarn.lock')
+    );
+  }
+
   run(
     root,
     appName,