[bugfix] Add i18n setup files to knip ignore list

These files are only used by playwright.i18n.config.ts for the collect-i18n script.
Knip doesn't recognize them as used since they're only referenced as string paths
in the Playwright config.

knip.config.ts

@@ -38,6 +38,9 @@ const config: KnipConfig = {
     // Test setup files
     'browser_tests/globalSetup.ts',
     'browser_tests/globalTeardown.ts',
+    'browser_tests/globalSetupWithI18n.ts',
+    'browser_tests/globalTeardownWithI18n.ts',
+    'browser_tests/i18nSetup.ts',
     'browser_tests/utils/**',
     // Scripts
     'scripts/**',