build iOS app on github actions

[gwennlbh]

seems possible, see https://medium.com/@olubusadea/how-i-built-an-ios-ci-cd-pipeline-without-a-mac-using-github-actions-e0766f8b3263

https://github.com/olubusade/mobile-ops-pro/blob/main/ci-architecture/workflows/ios-deploy.yml