Add Changes project URL (#24)

Co-authored-by: Andrew Svetlov <[email protected]>

Author: scop

setup.cfg

@@ -4,6 +4,7 @@ version = attr: pytest_aiohttp.__version__
 url = https://github.com/aio-libs/pytest-aiohttp
 project_urls =
   GitHub = https://github.com/aio-libs/pytest-aiohttp
+  Changelog = https://github.com/aio-libs/pytest-aiohttp/blob/master/CHANGES.rst
 description = Pytest plugin for aiohttp support
 long_description = file: README.rst
 long_description_content_type = text/x-rst