feat(nix): Add cargo-tarpaulin

flake.nix

@@ -27,11 +27,18 @@
 
         devShell = pkgs.mkShell {
           buildInputs = with pkgs; [openssl];
-          nativeBuildInputs = with pkgs; [rustc cargo rustfmt rust-analyzer pkg-config clippy];
+          nativeBuildInputs = with pkgs; [
+            rustc
+            cargo
+            rustfmt
+            rust-analyzer
+            pkg-config
+            clippy
+            cargo-tarpaulin
+          ];
         };
 
         formatter = nixpkgs.legacyPackages.${system}.alejandra;
       }
     );
 }
-