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

**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.