add options() method, resolve #2

tests/Pest/InvokableCasesTest.php

@@ -0,0 +1,19 @@
+<?php
+
+use ArchTech\Enums\Exceptions\UndefinedCaseError;
+
+it('can be used as a static method', function () {
+    expect(Status::PENDING())->toBe(0);
+    expect(Status::DONE())->toBe(1);
+});
+
+it('can be invoked as an instance', function () {
+    $status = Status::PENDING;
+
+    expect($status())->toBe(0);
+    expect($status())->toBe($status->value);
+});
+
+it('throws an error when a nonexistent case is being used', function () {
+    Status::INVALID();
+})->expectException(UndefinedCaseError::class);