Add Python 3.13 classifier to show it is supported (#72)

Author: singiamtel

pyproject.toml

@@ -24,6 +24,7 @@ classifiers = [
     "Programming Language :: Python :: 3.10",
     "Programming Language :: Python :: 3.11",
     "Programming Language :: Python :: 3.12",
+    "Programming Language :: Python :: 3.13",
     "Topic :: Documentation",
     "Topic :: Software Development :: Documentation",
     "Topic :: Text Processing :: Markup :: Markdown",