Rename actions, add action descriptions, update Readme

[stas-fomenko]

For component

• Update according to existing README template
• add API docs link: https://mailchimp.com/developer/reference/

For each action:
1.
Rename Unsubscribe Action -> Archive a list member
Add action description: Use this action in order to archive a list member.
Add to readme that it use method : DELETE /lists/{list_id}/members/{subscriber_hash} Archive a list member`

Rename Add new Subscriber Action -> Upsert a list member
Add action description: Use this action in order to add or update a list member
Add to readme that it use method : PUT | /lists/{list_id}/members/{subscriber_hash} | Add or update a list member`

Rename Upsert customer action -> Upsert a customer
Add action description: Use this action in order to add or update a customer
Add to readme that it use method: PUT | /ecommerce/stores/{store_id}/customers/{customer_id} | Add or update a customer`