Add links to make PyPI a better maintainer reference

[pydanny]

Following the conventions I discovered/documented here on the next PyPI release this adds links that make it easier for consumers of this project to see what changes may have occurred.

Thanks for a great project!

[pydanny]

Closing this because poetry has a different schema than what PyPI accepts for extra sidelinks.

[pydanny]

Reopening because someone pointed out to me this documentation reference.