Support for Android @NonNull and @Nullable annotations

[ILikeYourHat]

Hi! 😄

It would be very helpful for me if this plugin could support NonNull and Nullable annotations from android.support.annotation. Logic would be pretty simple: if a field is marked as "NonNull", then the corresponding builder method parameter would be also marked as "NonNull". Same thing for "Nullable". It should generate similar code to JSR-305 NonNull annotation.

Thanks in advance! 😄

[baolongnt]

Update: Android has now migrated to use these annotations instead:
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;