Add roles to organization member call

[larsf96]

Checklist

• I have looked into the Readme and Examples, and have not found a suitable solution or answer.
• I have looked into the API documentation and have not found a suitable solution or answer.
• I have searched the issues and have not found a suitable solution or answer.
• I have searched the Auth0 Community forums and have not found a suitable solution or answer.
• I agree to the terms within the Auth0 Code of Conduct.

Describe the problem you'd like to have solved

A few weeks ago, Auth0 has announced that the Management API can now directly return the user's roles within an organization (https://auth0.com/changelog#78X6urpiHJK6SY0fUw4zyh). Currently we have to do a lot of API calls with this library to get all users including their roles.
It's not yet possible to get the roles with mgmt.organizations().getMembers() as this property is missing.

Describe the ideal solution

The roles should be implemented to the Member class

Alternatives and current workarounds

No response

Additional context

No response

[jimmyjames]

Good timing @larsf96! We had this in our backlog for this week ;)

I've made #574, feel free to check it out!