test: add vitest for unit tests (#50)

* feat: add vitest for unit tests

* chore: address pull request feedback

* test: add unit test code quality workflow

packages/common/src/test/string.spec.ts

@@ -0,0 +1,19 @@
+import { describe, expect, it } from "vitest";
+
+import { capitalize } from "../string";
+
+const capitalizeTestCases = [
+  ["hello", "Hello"],
+  ["World", "World"],
+  ["123", "123"],
+  ["a", "A"],
+  ["two words", "Two words"],
+] as const;
+
+describe("capitalize should capitalize the first letter of a string", () => {
+  capitalizeTestCases.forEach(([input, expected]) => {
+    it(`should capitalize ${input} to ${expected}`, () => {
+      expect(capitalize(input)).toEqual(expected);
+    });
+  });
+});