feat: add string utility tests and vitest browser configuration

vitest.browser.config.ts

@@ -0,0 +1,18 @@
+import { defineConfig } from 'vitest/config'
+import { playwright } from '@vitest/browser-playwright'
+
+export default defineConfig({
+  test: {
+    browser: {
+      enabled: true,
+      provider: playwright(),
+      // https://vitest.dev/config/browser/playwright
+      instances: [
+        { name: 'chromium', browser: 'chromium' },
+      ],
+      locators: {
+        testIdAttribute: 'id',
+      },
+    },
+  },
+})