build: add test-ci package for local nix workflow testing

Author: albertodvp

.gitignore

@@ -13,4 +13,4 @@ vendor/
 .direnv
 result
 .pre-commit-config.yaml
-.pre-commit-config.yaml
+*.log

flake.nix

@@ -85,6 +85,14 @@
           go-jsonschema-go124 = makePackage pkgs.go_1_24;
           go-jsonschema-go125 = makePackage pkgs.go;
           default = makePackage pkgs.go;
+
+          test-ci = pkgs.writeShellApplication {
+            name = "test-ci";
+            runtimeInputs = [pkgs.act];
+            text = ''
+              exec act -W .github/workflows/nix.yaml -P ubuntu-24.04=catthehacker/ubuntu:act-24.04 "$@"
+            '';
+          };
         };
 
         checks = {