Adding the playable graph visualizer package to project

Packages/manifest.json

     "com.unity.ide.visualstudio": "1.0.11",
     "com.unity.ide.vscode": "1.0.7",
     "com.unity.package-manager-ui": "2.2.0",
+    "com.unity.playablegraph-visualizer": "0.2.1-preview.3",
     "com.unity.render-pipelines.lightweight": "6.5.2",
     "com.unity.test-framework": "1.0.13",
     "com.unity.textmeshpro": "2.0.1",