Add VM configuration files as a submodule

Author: Mingyumaz

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "vm"]
+	path = vm
+	url = https://github.com/p4lang/tutorials.git

README.md

@@ -1,3 +1,8 @@
 # p4 simulator module
 
-[Quick Note with Google Docs](https://docs.google.com/document/d/18QQqo4PK8ycuZovrbAacRtFtqWSIqS0v9hRiiUYgvU8/edit?usp=sharing)
+[Quick Note with Google Docs](https://docs.google.com/document/d/18QQqo4PK8ycuZovrbAacRtFtqWSIqS0v9hRiiUYgvU8/edit?usp=sharing)
+
+
+## Virtual Machine
+
+`p4sim` integrates an NS-3-based P4 simulation environment with virtual machine configuration files sourced via sparse checkout from the [P4Lang tutorials repository](https://github.com/p4lang/tutorials/tree/master). The `vm` directory contains setup files, including Vagrant configurations and bootstrap scripts, for Ubuntu-based virtual machines (`20.04` and `24.04`) that simplify the process of installing NS-3 and its dependencies. Using these pre-configured virtual machines is highly recommended for a streamlined setup, ensuring compatibility and minimizing installation issues.