Update Github Action and README

[supermaxiste]

Dear @ashleycaselli,

thank you for taking over the SHACL API repository and doing such a tidy job for the new release :)

In this PR I'm changing the README as follows:

• update all mentions of 1.4.2 to 1.4.3
• minor fix on the arm base image when building a local Dockerfile

The PR also includes changes to the Github Action file as follows:

• update all Actions to their latest version (this addresses a deprecation warning related to Github transitioning to a new node)
• small refactoring of the actions related to download/upload of artifacts (inspired by this reply from this issue)

[ashleycaselli]

Thanks @supermaxiste for your contribution.