Upgrade to Angular 16 and official jest builder

Because I could not make @angular-builders/jest work and Angular 15 is
EOL in a few days anyway.

README.md

@@ -8,7 +8,7 @@
 
 ### Upgrade instructions
 For a list of breaking changes and update instructions, go to [releases](https://github.com/Mawi137/ngx-image-cropper/releases).
-Only Angular 15+ is supported.
+Only Angular 16+ is supported.
 
 ### Example usage
 Add the ImageCropperModule to the imports of the module which will be using the Image Cropper.

angular.json

@@ -25,9 +25,13 @@
           "defaultConfiguration": "production"
         },
         "test": {
-          "builder": "@angular-builders/jest:run",
+          "builder": "@angular-devkit/build-angular:jest",
           "options": {
-            "tsConfig": "tsconfig.spec.json"
+            "tsConfig": "projects/ngx-image-cropper/tsconfig.spec.json",
+            "polyfills": [
+              "zone.js",
+              "zone.js/testing"
+            ]
           }
         }
       }
@@ -49,7 +53,7 @@
             "outputPath": "dist/demo-app",
             "index": "projects/demo-app/src/index.html",
             "main": "projects/demo-app/src/main.ts",
-            "polyfills": "projects/demo-app/src/polyfills.ts",
+            "polyfills": ["zone.js"],
             "tsConfig": "projects/demo-app/tsconfig.app.json",
             "inlineStyleLanguage": "scss",
             "assets": [