Update the publiccode.yaml releaseDate automatically on new builds

[Abbe98]

The feature

Write a Github Action which triggers on pushes to the gh-pages branch and then updates the publiccode.yaml.

[RVA2869]

And (if possible) add the ISO 3166-1 alpha-2 code (P297).
Or this could be a manual thing.

intendedAudience:
  
  countries:
    - at
    - be
    - ca
    - cz
    - dk
    - tl
    - fi
    - de
    - gh
    - gl
    - is
    - in
    - id
    - lu
    - my 
    - mt
    - ma
    - np
    - nl
    - nz
    - no
    - pe
    - ph
    - ru
    - sg
    - za
    - se
    - ua
    - gb