fix: allow for lower python version

Author: codcod

pyproject.toml

@@ -3,7 +3,7 @@ name = "smppai"
 version = "0.1.0"
 description = "Async SMPP (Short Message Peer-to-Peer) Protocol v3.4 Implementation"
 readme = "README.md"
-requires-python = ">=3.13"
+requires-python = ">=3.8"
 classifiers = [
     "Development Status :: 3 - Alpha",
     "Topic :: Software Development :: Libraries :: Python Modules",