Add build argument VERSION

[markusweigelt]

To build the stable version for our integration repository, we need the version specification similar to the OCR-D Controller.

[bertsky]

Please add the recipe for passing VERSION in the CI builds as you have already done in the Controller:

• as workflow input variable
• as cache key
• as build arg

[markusweigelt]

@bertsky Thx for the feedback. It's done :)

[bertsky]

superb!