feat(devshell): Add pkgs for helix and switching to zsh

flake.nix

@@ -125,9 +125,12 @@
     devShells."${system}".default = let
       pkgs = import nixpkgs { inherit system; };
     in pkgs.mkShell {
+      shellHook = "zsh";
       packages = with pkgs; [
         cargo
         rustc
+        rust-analyzer
+        lldb
       ];
     };
   };