Add Free Threading in pyproject.toml

Author: bangseongbeom

pyproject.toml

@@ -23,6 +23,7 @@ classifiers = [
     "Programming Language :: Python :: 3.13",
     "Programming Language :: Python :: 3.14",
     "Programming Language :: Python :: 3 :: Only",
+    "Programming Language :: Python :: Free Threading",
     "Programming Language :: Python :: Implementation :: CPython",
     "Programming Language :: Python :: Implementation :: PyPy",
     "Programming Language :: Rust",