support custom localization

[ansoncsh]

Added an optional parameter "locale" to the class "OnfidoConfig" to support custom locaalization.

If the parameter "locale" is passed, the custom translations of the locale can be loaded.

Custom translations can be maintained by following the guides of the official SDK documentations:

• Android: https://documentation.onfido.com/sdk/android/#localization
• iOS: https://documentation.onfido.com/sdk/ios/#language-customization

[geweald]

Thank you @ansoncsh can you resolve conflicts and add a changelog + bump version number?

[ansoncsh]

@geweald the conflicts are resolved. changelog + version number are also updated

Thanks a lot.