Implement overload ban method.

[kiLeo13]

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Changes

• [ ] Internal code
• [x] Library interface (affecting end-user code)
• [x] Documentation
• [ ] Other: _____

Closes Issue: NaN

Description

Added an overload ban() method in the Member interface that allows banning a member without deleting any messages sent by the user.

Included Javadoc for new Member#ban() method and updated Javadoc for method Member#ban(int, TimeUnit), suggesting users to use the overload method if no messages are meant to be deleted.