Fixes the missing source_url warning raised by jaraco.packaging.sphinx

Version 10.4.0 of jaraco.packaging.sphinx introduced the requirement to
provide a source_url. This commit adds it to pyproject.toml.

Author: julianz-

pyproject.toml

@@ -61,6 +61,7 @@ email = "team@cherrypy.dev"
 
 [project.urls]
 Homepage = "https://cheroot.cherrypy.dev"
+"Source" = "https://github.com/cherrypy/cheroot"
 "Chat: Matrix" = "https://matrix.to/#/#cherrypy-space:matrix.org"
 "CI: GitHub" = "https://github.com/cherrypy/cheroot/actions"
 "Docs: RTD" = "https://cheroot.cherrypy.dev"