feat(pwa): make the app installable

Manifest, gamepad icon (also the new favicon, instead of
the Vite logo), iOS meta tags and the tab title
ToBePlayed. No service worker, so a deploy never meets
an old cached bundle. The title bar color follows
light and dark mode. The README also lists adding a
game by name.

src/context/PreferencesContext.test.jsx

@@ -0,0 +1,35 @@
+// @vitest-environment jsdom
+import {afterEach, beforeEach, describe, expect, it, vi} from 'vitest';
+import {act, cleanup, render} from '@testing-library/react';
+import {PreferencesProvider, usePreferences} from './PreferencesContext.jsx';
+
+vi.mock('react-i18next', () => import('../test/i18n-mock.js'));
+
+let preferences;
+function Spy() {
+    preferences = usePreferences();
+    return null;
+}
+
+const themeColor = () => document.querySelector('meta[name="theme-color"]').content;
+
+beforeEach(() => {
+    document.head.innerHTML = '<meta name="theme-color" content="#09090b">';
+});
+
+afterEach(() => {
+    cleanup();
+    localStorage.clear();
+});
+
+describe('PreferencesProvider theme color', () => {
+    it('gives the installed app a light title bar in light mode and a dark one again in dark mode', () => {
+        localStorage.setItem('tbp_dark_mode', 'false');
+        render(<PreferencesProvider><Spy/></PreferencesProvider>);
+
+        expect(themeColor()).toBe('#fafafa');
+
+        act(() => preferences.setDarkMode(true));
+        expect(themeColor()).toBe('#09090b');
+    });
+});