add multiplayer playmode package

Adds com.unity.multiplayer.playmode 2.0.2 (manifest + lock) for local multi-client testing. Serializes the package's generated PlayMode.meta and VirtualProjectsConfig.json.

Co-Authored-By: Claude <noreply@anthropic.com>

Assets/Settings/PlayMode.meta

@@ -0,0 +1,8 @@
+fileFormatVersion: 2
+guid: 356e0b9de894a0349a1537ff80a01207
+folderAsset: yes
+DefaultImporter:
+  externalObjects: {}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: