feat: add toBeUlid assertion and isUlid validation method (#1726)

src/Support/Str.php

@@ -98,6 +98,14 @@ final class Str
         return preg_match('/^[\da-f]{8}-[\da-f]{4}-[\da-f]{4}-[\da-f]{4}-[\da-f]{12}$/iD', $value) > 0;
     }
 
+    /**
+     * Determine if a given value is a valid ULID.
+     */
+    public static function isUlid(string $value): bool
+    {
+        return preg_match('/^[0-9A-HJKMNP-TV-Z]{26}$/', $value) > 0;
+    }
+
     /**
      * Creates a describe block as `$describeDescription` → `$testDescription` format.
      *