setup.cfg: declare project urls

setup.cfg

@@ -6,6 +6,10 @@ author      = Felix Schwarz
 author_email = felix.schwarz@oss.schwarz.eu
 license     = MIT
 home-page   = https://github.com/FelixSchwarz/pycerberus
+project_urls =
+    Source Code = https://github.com/FelixSchwarz/pycerberus
+    Bug Tracker = https://github.com/FelixSchwarz/pycerberus/issues
+    Documentation = https://pycerberus.readthedocs.io
 classifiers =
     Development Status :: 4 - Beta
     Intended Audience :: Developers
@@ -15,6 +19,7 @@ classifiers =
     Programming Language :: Python :: 3
     Topic :: Software Development :: Libraries :: Python Modules
 
+
 [options]
 packages = find:
 # simple_super is not zip_safe, neither is the current gettext implementation