A selector which always provides a constant value.
constSelector may be useful if you have an interface that uses a type such as
RecoilValueReadOnly<T> that may be provided by different selector implementations.
These selectors will memoize based on reference value equality. So,
constSelector() can be called multiple times with the same value and the same selector will be provided. Because of this, the value used as a constant is restricted to types that may be serialized using the Recoil serialization. Please see documentation in
selectorFamily describing the limitations.