make properties explicitly nullable (#78)

* made external id explicitly nullable

* fix: make constructor parameters explicitly nullable to avoid deprecation warnings

---------

Co-authored-by: Maarten Paauw <github@paauw.dev>

Author: krb19xx

src/Exception.php

@@ -14,7 +14,7 @@ class Exception extends RuntimeException
     /**
      * @param array<string|int> $args
      */
-    public function __construct(string $message, array $args = [], Throwable $previous = null)
+    public function __construct(string $message, array $args = [], ?Throwable $previous = null)
     {
         $message = $args ? vsprintf($message, $args) : $message;
 

src/Hydration/HydrationException.php

@@ -12,7 +12,7 @@ class HydrationException extends Exception
     /**
      * @param array<string|int> $args
      */
-    public function __construct(string $message, array $args = [], Throwable $previous = null)
+    public function __construct(string $message, array $args = [], ?Throwable $previous = null)
     {
         parent::__construct("FromArray Error: {$message}", $args, $previous);
     }

src/Kit.php

@@ -120,7 +120,7 @@ public static function divider(?string $blockId = null): Blocks\Divider
     }
 
     public static function file(
-        string $externalId = null,
+        ?string $externalId = null,
         ?string $source = 'remote',
         ?string $blockId = null,
     ): Blocks\File {