Add dprint to devcontainer (microsoft#55581)

Author: jakebailey

.devcontainer/devcontainer.json

@@ -18,9 +18,10 @@
                 }
             },
             "extensions": [
-                "dbaeumer.vscode-eslint"
+                "dbaeumer.vscode-eslint",
+                "dprint.dprint"
             ]
         }
     },
     "remoteUser": "node"
-}
+}