build: bump to 0.4.0 and update Python support

- Bump version from 0.3.0 to 0.4.0
- Remove Python 3.7 and 3.8 support
- Add Python 3.11, 3.12, and 3.13 support
- Update python_requires from >=3.7 to >=3.9
- Update tox env_list to test py39-py313

Aligns with C2PA spec v2.2 upgrade and ubuntu-latest support

Author: olgahaha

setup.cfg

@@ -1,6 +1,6 @@
 [metadata]
 name = numbers-c2pa
-version = 0.3.0
+version = 0.4.0
 author = Numbers Co., Inc
 author_email = [email protected]
 description = Numbers C2PA tool
@@ -11,16 +11,17 @@ url = https://github.com/numbersprotocol/numbers-c2pa
 classifiers =
     Development Status :: 4 - Beta
     License :: OSI Approved :: MIT License
-    Programming Language :: Python :: 3.7
-    Programming Language :: Python :: 3.8
     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
 
 [options]
 package_dir=
     =src
 zip_safe = True
-python_requires = >=3.7
+python_requires = >=3.9
 packages = find:
 install_requires =
     cryptography
@@ -68,7 +69,7 @@ exclude = .git,__pycache__,__init__.py,.mypy_cache,.pytest_cache,venv,.venv
 
 [tox:tox]
 env_list=
-    py38, py39, py310, flake8, pylint, bandit, test, report
+    py39, py310, py311, py312, py313, flake8, pylint, bandit, test, report
 
 [testenv]
 deps =