Add release guide to dev guide

[jbreue16]

We should document necessary steps to make a new release in the dev guide

1. run the release CI (python scripts in cadet-reference ) ... ?) The release commit should be "Bump version to ?.?.?", similar to 276 ?) How to create and upload binaries to conda forge; Build configurations (e.g. multithreading disabled)

[schmoelder]

We have a (somewhat up-to-date) guide in the Forum: https://forum.cadet-web.de/t/how-to-make-a-new-cadet-release/401

[jbreue16]

Fixed per #319