Add support for withoutScopedBindings to ScopeBindings attribute.

[mikerockett]

This is a continuation of #134, with two adjustments:

1. Given the recent drop of support for Laravel 8 and 9 (521ba0e), there is no need to check whether or not withoutScopedBindings is an existing method.
2. Tests cater for method-level opt-ins (where the controller defaults to opt-out).

README.md is also updated with changes in behaviour.

[freekmurze]

Thanks!