build: Drop Python 3.9 support. Add Python 3.13 support.

Author: jpmckinney

.github/workflows/ci.yml

@@ -9,7 +9,7 @@ jobs:
     strategy:
       matrix:
         os: [macos-latest, windows-latest, ubuntu-latest]
-        python-version: [3.9, '3.10', '3.11', '3.12']
+        python-version: ['3.10', '3.11', '3.12', '3.13']
     steps:
       # Prevent Git from changing LF to CRLF, which affects test fixtures.
       - run: git config --global core.autocrlf false

pyproject.toml

@@ -13,10 +13,10 @@ urls = {Homepage = "https://github.com/open-contracting/cardinal-rs"}
 classifiers = [
     "License :: OSI Approved :: MIT License",
     "Operating System :: OS Independent",
-    "Programming Language :: Python :: 3.9",
     "Programming Language :: Python :: 3.10",
     "Programming Language :: Python :: 3.11",
     "Programming Language :: Python :: 3.12",
+    "Programming Language :: Python :: 3.13",
     "Programming Language :: Python :: Implementation :: CPython",
     "Programming Language :: Rust",
 ]