Add Python 3.15 to classifiers

Author: Евгений Блинов

pyproject.toml

@@ -28,6 +28,7 @@ classifiers = [
     'Programming Language :: Python :: 3.12',
     'Programming Language :: Python :: 3.13',
     'Programming Language :: Python :: 3.14',
+    'Programming Language :: Python :: 3.15',
     'Programming Language :: Python :: Free Threading',
     'Programming Language :: Python :: Free Threading :: 3 - Stable',
     'License :: OSI Approved :: MIT License',