Add continuous deployment (CD) pipeline

[schuenke]

An automatic deployment to PyPi and conda would be great in the future. We still need to discuss:

• when should this be triggered (push to main / taged pushed / etc)
• do we want to give automatic versioning a try?
• do we want to create automatic changelogs?
• which conda server do we want to use? conda-forge? requirements for that?
• ...

[ckolbPTB]

linked to #125