Improve documentation on additional role assigments and examples

[baatch]

Describe the solution you'd like

The documentation for adding additional role requirements at https://github.com/Azure/data-management-zone/blob/main/docs/EnterpriseScaleAnalytics-ServicePrincipal.md#adding-additional-role-assigments
could be improved by adding additional text to describe that the role assignments should be done on either resource or resource group level. Also clear examples in the code examples with values makes it easier to follow and understand.

See discussion with marvibuss here #199

[marvinbuss]

@esbran and @amanjeetsingh can you please take a look and discuss how we can improve?
Please also check this to understand the issue: #199

[marvinbuss]

The same must be done from all other repos: Data Landing Zone, Data Product xyz.

[marvinbuss]

@kbhatiaGIT was mentioning as well that this is confusing. Can you please update this in the following weeks?