Add strict types declaration

Author: adriansuter

src/Cache.php

@@ -5,6 +5,8 @@
  * @license   https://github.com/slimphp/Slim-HttpCache/blob/master/LICENSE.md (MIT License)
  */
 
+declare(strict_types=1);
+
 namespace Slim\HttpCache;
 
 use Psr\Http\Message\ResponseInterface;

src/CacheProvider.php

@@ -5,6 +5,8 @@
  * @license   https://github.com/slimphp/Slim-HttpCache/blob/master/LICENSE.md (MIT License)
  */
 
+declare(strict_types=1);
+
 namespace Slim\HttpCache;
 
 use InvalidArgumentException;

tests/CacheProviderTest.php

@@ -5,6 +5,8 @@
  * @license   https://github.com/slimphp/Slim-HttpCache/blob/master/LICENSE.md (MIT License)
  */
 
+declare(strict_types=1);
+
 namespace Slim\HttpCache\Tests;
 
 use InvalidArgumentException;

tests/CacheTest.php

@@ -5,6 +5,8 @@
  * @license   https://github.com/slimphp/Slim-HttpCache/blob/master/LICENSE.md (MIT License)
  */
 
+declare(strict_types=1);
+
 namespace Slim\HttpCache\Tests;
 
 use PHPUnit\Framework\TestCase;

tests/bootstrap.php

@@ -5,4 +5,6 @@
  * @license   https://github.com/slimphp/Slim-HttpCache/blob/master/LICENSE.md (MIT License)
  */
 
+declare(strict_types=1);
+
 require __DIR__.'/../vendor/autoload.php';