Token support

Problem/Motivation

For a module extending the functionality of crm_membership, I need to have support for Tokens.
The contrib Token module provides default token integration for content entities, so crm_membership and crm_membership_period entities are covered automatically by adding a dependency to contrib Token module.

For crm_membership_type config entity this is not the case, since contrib Token module doesn't provide functionality for config entities.

Proposed resolution

Add explicit token support for crm_membership_type config entities.