Clarify and document what the 3D Secure options do

Problem/Motivation

Clarify and document what the 3D Secure options do
The 3D Secure has 3 options

• Disabled
• Enabled
• Required

It will be helpful to add a description and more information in the readme file.
My understanding is as follows:

• These options only control the behaviour of Drupal handling of 3D Secure and not the underlying Braintree functionality.
• Disabled - This will disable the display of the 3D Security check but not the requirement set on the Braintree account and can result in failed transactions.
• Enabled - Normal behaviour Braintree to determine. By default, it follows the "Reject if 3DS is required" rules
• Required - If "Liability Shifted" is False, disallow the transaction. Braintree may allow the transactions if "Reject if 3DS is required" evaluates to FALSE but Drupal will reject if "Liability Shifted" is False.

Not at all sure if I am correct and it will be great to get feedback and document this for the benefit of other users.