Automated creation and publishing of flux-commands.md

[fsteeg]

This is part of https://github.com/metafacture/metafacture.github.io/issues/10

Automated creation and publishing of flux-commands.md (which is basically the output of sh flux.sh > flux-commands.md, see https://github.com/metafacture/metafacture-core/commit/4d80ab4a87eed552fb36de722765c2f1ae6e7923; Java implementation is in HelpPrinter.java):

• [ ] Create flux-commands.md with GitHub Actions (triggered by push to main branch)
• [ ] Push flux-commands.md to metafacture.github.io in docs/main with GitHub Actions
• [ ] Set up mechanism for release documentation at e.g. docs/5.2.0 & alias docs/latest