Function addWithdrawal

Immutably adds or updates a withdrawal entry in a withdrawals map.

This function takes an existing withdrawals map and returns a new map containing all original entries plus the new or updated one. The original map is not modified.

let withdrawals: Withdrawals = {};
withdrawals = addWithdrawal(withdrawals, 'stake1u89s33n55j2xv58qj7jklp9z5f4q9c9..., 1000000n);
withdrawals = addWithdrawal(withdrawals, 'stake1u98s33n55j2xv58qj7jklp9z5f4q9c9...', 2500000n);
// withdrawals is now {
// 'stake1u89s33n55j2xv58qj7jklp9z5f4q9c9...': 1000000n,
// 'stake1u89s33n55j2xv58qj7jklp9z5f4q9c9...': 2500000n
// }