docs: Add documentation for all modules to help the user when using it

[mcruzdev]

What would you like to be added:

Add documentation for every module, for helping the new contributors/users.

We can easily to add as pom.xml simbling a README.md file, explaning all relevant detais about a module.

Why is this needed:

For helping new users/contributors to use in a frictionless way the module.

[fjtirado]

Yes, also we need to update the module description on the main readme https://github.com/serverlessworkflow/sdk-java/blob/main/impl/README.md?plain=1#L79-L86