CI build package using actions

[slamora]

Main changes

• Update README.md with updated build instructions.
• Configure GitHub actions to build package & store as artifact (build.zip file).

Questions/to be discussed

• [x] Which environment do you prefer to build it? (e.g. e4)
• [x] When do you want that the module is built? (e.g. on any branch pushed to this repository, only branches related to a pull request...) NOW is built on every push.

NOTE: build.zip is available on the Actions page. E.g. 1ba5b16 build

[slamora]

Sorry @forste , I never reply your questions.

Regarding your questions, can the build action be connected to a deployment action?

Yes, it can.

If so, then it might make sense to build for the appropriate environment and with appropriate settings when changing the master or testing branches and then automatically deploy to the respective server

I've adapted the config.yml and the actions to follow your suggestion on the build step.

Regarding automatic deploy, I will check about the posibilities.

[slamora]

Please @forste could you merge this PR? I will continue the CD work on another branch, thanks!