Use TS for example

Author: jessealama

examples/mortgage.js examples/mortgage.ts

@@ -1,17 +1,17 @@
 import { Decimal128 } from "../src/decimal128.mjs";
-import { pow } from "./pow.js";
+import { pow } from "./pow.mjs";
 
 const one = new Decimal128("1");
 const paymentsPerYear = new Decimal128("12");
 
-function calculateMonthlyPayment(p, r, y) {
+function calculateMonthlyPayment(p: string, r: string, y: string): Decimal128 {
     const principal = new Decimal128(p);
     const annualInterestRate = new Decimal128(r);
     const years = new Decimal128(y);
     const monthlyInterestRate = annualInterestRate.divide(paymentsPerYear);
     const paymentCount = paymentsPerYear.multiply(years);
     const onePlusInterestRate = monthlyInterestRate.add(one);
-    const ratePower = pow(onePlusInterestRate, paymentCount);
+    const ratePower = pow(onePlusInterestRate, Number(paymentCount));
 
     const x = principal.multiply(monthlyInterestRate);