AsReadonlyView extension method

[JohanLarsson]

var view = foo.ObserveValue(x => x.Items).AsReadOnlyView();

[JohanLarsson]

Workaround 1:

var view = foo.ObserveValue(x => x.Items)
              .Select(x => x.GetValueOrDefault())
              .AsReadOnlyView()

Workaround 2:

var view = foo.ObserveValue(x => x.Items)
              .Select(x => (IMaybe<int[]>)x)
              .AsReadOnlyView()

We can add ObserveEnumerableValue() that returns IMaybe<IEnumerable<T>> but not sure it is worth it.

Another alternative is to generate overloads for common collection types but it will not work for immutable collections which is a common use case.

[JohanLarsson]

Not doing anything with this, chances are shapes will solve it in the future.