Make Java dependency explicit

[georghinkel]

Hi,

given that not everybody in the MDE community always works with Java, could you be so kind to make the technological requirements explicit in the readme? I experienced the following:

• You need to have a GitHub personal access token set to read:packages, otherwise Gradle fails to resolve the dependencies
• You need to use JDK 17, because Gradle does not support JDK 19 or newer

Best,

Georg