New accessor function to get all the store contents as a flat object

[kabirbaidhya]

New accessor function (eg: getAll) to get all the store contents as a flat object.

Example:

const a = 1;
const b = 2;
const sum = a + b;

store.set({ a, b });
store.set({ sum });

console.log('Store contents:', store.getAll());
// > Store contents: { a: 1, b: 2, sum: 3 }