Use yarn v3.

Author: CXuesong

graywing-client/.gitignore

@@ -37,3 +37,11 @@ testem.log
 # System Files
 .DS_Store
 Thumbs.db
+
+.pnp.*
+.yarn/*
+!.yarn/patches
+!.yarn/plugins
+!.yarn/releases
+!.yarn/sdks
+!.yarn/versions

graywing-client/.yarn/releases/yarn-3.3.0.cjs

@@ -0,0 +1,3 @@
+yarnPath: .yarn/releases/yarn-3.3.0.cjs
+
+nodeLinker: node-modules

graywing-client/.yarnrc.yml

@@ -51,5 +51,6 @@
     "ts-node": "^8.3.0",
     "tslint": "~6.1.0",
     "typescript": "~4.3.5"
-  }
+  },
+  "packageManager": "yarn@3.3.0"
 }