Add TargetKind.getter item to @Target attribute for PreResolve

[bambinoua]

After new flutter_lints installed I get this message on pre-resolved getters:

The annotation 'preResolve' can only be used on methods.

It wouild be good to add TargetKind.getter to @Target attribute for PreResolve.

@Target({TargetKind.method})
class PreResolve {
  const PreResolve._();
}