Add API scaffolding to the template; fix placeholder description

[HafizMMoaz]

Closes zerp-pk/package-template#37.

New modules copied from this template now start API-ready instead of web-only.

Changes

• composer.json — replaced "Description for example-package package" with a real one-line description.
• src/Routes/api.php — the api.json + auth:sanctum group under the module slug, matching every other Zerp module (hrm, lead, taskly...), with a sample route wired up.
• src/Http/Controllers/Api/ExamplePackageItemApiController — a sample controller returning a typed JsonResource collection (: AnonymousResourceCollection), the shape that gives Scramble a real response schema rather than an opaque object. Ties into zerp-pk/hrm#34's direction so new modules adopt the rich-OpenAPI pattern from day one.
• src/Http/Resources/ExamplePackageItemResource — the resource whose typed, one-per-line fields Scramble reads.
• ServiceProvider — loads api.php, plus a commented Scramble::registerApi(...) block to uncomment and rename once real endpoints exist (guarded with class_exists, exactly as hrm does it).

Verification

• php -l clean on all new/changed files.
• composer validate passes.
• Existing template test suite still green (2 tests) — the provider boots with api.php loaded.

The sample controller extends App\Http\Controllers\Controller and uses App\Traits\ApiResponseTrait, which resolve inside the host app (the same as hrm's API controllers); route loading does not autoload the controller, so the isolated testbench suite is unaffected.