Add automatic testing of modules

[badlop]

It would be great if the modules in ejabberd-contrib (and the ones in extra/) could be automatically tested for every push and PR.

Some ideas to check for each module:

• [x] module compiles correctly (can be installed)
• [ ] module compilation doesn't throw warnings
• [ ] module can be uninstalled and doesn't throw warnings or errors
• [x] module succeeds "make xref"
• [ ] module succeeds "make dialyzer"
• [x] if any module fails any test, return error and let know which one failed and why

For all this, the corresponding Github Action would need to download the latest ejabberd from git, compile, start, and then run "module_install" for all the modules that aren't marked as broken