add 'release' workflow to GH actions

[JuliaSprenger]

to speed up the neo release cycle it would help to have a workflow for this. This would need to cover

• check documentation is compiling
• check core and io tests are running
• check package building
• check pushing and installing from test.pypi
• push to pypi

this workflow should only be triggered by tagged commits.

[JuliaSprenger]

for comprehensive testing of documentation building we could build the doc on actions and only push the resulting html to readthedocs