gh-124621: Emscripten: Add smoke test for using pyrepl in Chrome

This should make it less likely that we break Python startup in the
browser.

Author: hoodmane

Tools/wasm/emscripten/browser_test/.gitignore

@@ -0,0 +1,4 @@
+node_modules
+test-results
+playwright-report
+

Tools/wasm/emscripten/browser_test/index.spec.ts

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+import { test, expect } from '@playwright/test';
+
+test('has title', async ({ page }) => {
+  await page.goto('/');
+
+  await expect(page).toHaveTitle("Emscripten PyRepl Example");
+  const xterm = await page.locator('css=#terminal');
+  await expect(xterm).toHaveText(/Python.*on emscripten.*Type.*for more information/);
+  const xtermInput = await page.getByRole('textbox');
+  await xtermInput.pressSequentially(`def f():\nprint("hello", "emscripten repl!")\n\n`);
+  await xtermInput.pressSequentially(`f()\n`);
+  await expect(xterm).toHaveText(/hello emscripten repl!/);
+
+});
+