initializate client, server, shared

- initializated base structure of server
 - initializated base structure of client
 - initializated base structure of shared(lib for client and server)

shared/pubspec.yaml

@@ -0,0 +1,15 @@
+name: shared
+description: A starting point for Dart libraries or applications.
+version: 1.0.0
+# repository: https://github.com/my_org/my_repo
+
+environment:
+  sdk: ^3.11.1
+
+# Add regular dependencies here.
+dependencies:
+  # path: ^1.9.0
+
+dev_dependencies:
+  lints: ^6.0.0
+  test: ^1.25.6