Added nix flake and shell files for nixos users who want to work on development. You can use flake method => 'nix develop' or non flake method =>`nix-shell'

The shell.nix file is used for both flake and non-flake invocations. The lock file is also set at a version where the project works.
Note the none-flake method will follow the version of the system and isn't guaranteed to work on older installations if they haven't been updated in a while.
Added Documentation for using Nix package manager for development ./Documentation/LinuxDevelopmentSetupUsingNix.md

Signed-off-by: Ayman Jundi <ajundi@gmail.com>

shell.nix

@@ -0,0 +1,19 @@
+{pkgs ? import <nixpkgs> {}}: let
+  libPath = with pkgs;
+    lib.makeLibraryPath [
+      # load external libraries that you need in your dotnet project here
+      xorg.libX11
+      xorg.libICE
+      xorg.libSM
+      libGL
+      fontconfig
+    ];
+in
+  pkgs.mkShell {
+    buildInputs = with pkgs; [
+      dotnet-sdk_9
+    ];
+    
+    DOTNET_ROOT = "${pkgs.dotnet-sdk_9}/share/dotnet";
+    LD_LIBRARY_PATH =libPath;
+  }