Add references and usage for mpx-api-client

[0xean]

User Story

• As an <audience/user>: dev
• I want to <action/task>: know about how to use mpx-api-client
• so that <outcome/goal/benefit>: I can leverage the open source package

Type

• Enhancement
• Maintenance
• Refactor

Definition of Done

• add docs for mpx-api-client
• add usage informationas well