feat: add multiply function

src/index.ts

@@ -1,3 +1,4 @@
+export * from "./types.js";
 export * from "./greet.js";
 export * from "./sum.js";
-export * from "./types.js";
+export * from "./multiply.js";

src/multiply.test.ts

@@ -0,0 +1,20 @@
+import { describe, expect, it } from "vitest";
+import { multiply } from "./multiply.js";
+
+describe("multiply", () => {
+	it("multiplies two numbers", () => {
+		expect(multiply(2, 3)).toBe(6);
+	});
+
+	it("multiplies two negative numbers", () => {
+		expect(multiply(-2, -3)).toBe(6);
+	});
+
+	it("multiplies a positive and a negative number", () => {
+		expect(multiply(2, -3)).toBe(-6);
+	});
+
+	it("multiplies two floating point numbers", () => {
+		expect(multiply(1.1, 2.2)).toBeCloseTo(2.42);
+	});
+});

src/multiply.ts

@@ -0,0 +1,3 @@
+export function multiply(a: number, b: number): number {
+	return a * b;
+}