Creates a new Observe function that caches the last value, notifies every new observer
immediately with it, and shares a single upstream subscription across simultaneous observers.
By default the cache is reference-counted — see WithCacheOptions.release. Pass
{ release: false } to keep the upstream alive and retain the value for the observable's
lifetime, replaying it synchronously to every subscriber.
Creates a new Observe function that caches the last value, notifies every new observer immediately with it, and shares a single upstream subscription across simultaneous observers.
By default the cache is reference-counted — see WithCacheOptions.release. Pass
{ release: false }to keep the upstream alive and retain the value for the observable's lifetime, replaying it synchronously to every subscriber.