Migration guide from 4.x to 5.x

[sergionettl]

Is your feature request related to a problem? Please describe.

Website lacks a migration or documentation for the SDK v 5.x

https://developer.paypal.com/braintree/docs/guides/client-sdk/migration/android/v4

Describe the solution you'd like.

A page describing the migration (like is done in https://developer.paypal.com/braintree/docs/guides/client-sdk/migration/android/v4)

[saperi22]

@sergionettl checkout v5 migration guide. Hope this helps while we work on a migration guide on the official developer docs site.

[sergionettl]

thanks