Add tests for strict types expectation

Introduced new test cases to ensure strict type declaration handling. Files with and without strict types are tested, including scenarios with comments preceding the declaration. Updated the regex in `Expectation.php` to accommodate comments and whitespaces before the `declare(strict_types=1)` statement.

tests/Features/Expect/toUseStrictTypes.php

@@ -0,0 +1,18 @@
+<?php
+
+declare(strict_types=1);
+
+use Pest\Arch\Exceptions\ArchExpectationFailedException;
+use Tests\Fixtures\Arch\ToUseStrictTypes\HasNoStrictType;
+use Tests\Fixtures\Arch\ToUseStrictTypes\HasStrictType;
+use Tests\Fixtures\Arch\ToUseStrictTypes\HasStrictTypeWithCommentsAbove;
+
+test('pass', function () {
+    expect(HasStrictType::class)->toUseStrictTypes()
+        ->and(HasStrictTypeWithCommentsAbove::class)->toUseStrictTypes();
+});
+
+test('failures', function () {
+    expect(HasNoStrictType::class)->toUseStrictTypes();
+})->throws(ArchExpectationFailedException::class);
+