Merge method to return the part for this Observable to return.
OptionalmemoizationFunction: MemoizationFunction<R>Method to Compare if the merged data has changed. Should return true when data is different.
const mergedObservable = mergeObservables(
[observable1, observable2],
([value1, value2]) => value1 + value2,
);
if observable1 has the value of 10 and observable2 has the value of 4, the mergedObservable will return the value of 14.
if one of them changes the mergedObservable will return the new value.
an Array of Observables to merge for this Observable.