Check existence of the `window` object when setting window translations

What does this MR do and why?

Adds some additional checks for the window object in app/assets/javascripts/locale/index.js.

This prevents Uncaught ReferenceError: window is not defined errors when the i18n methods are imported into a Web worker context.

Screenshots or screen recordings

How to set up and validate locally

1. Apply this patch

diff --git a/app/assets/javascripts/lib/utils/text_utility.js b/app/assets/javascripts/lib/utils/text_utility.js
index 367180714dfb..9df871cdcfbc 100644
--- a/app/assets/javascripts/lib/utils/text_utility.js
+++ b/app/assets/javascripts/lib/utils/text_utility.js
@@ -1,4 +1,5 @@
 import { isString, memoize } from 'lodash';
+import { sprintf, __ } from '~/locale';
 import { base64ToBuffer, bufferToBase64 } from '~/authentication/webauthn/util';
 import {
   TRUNCATE_WIDTH_DEFAULT_WIDTH,
@@ -525,3 +526,5 @@ export function base64DecodeUnicode(str) {
   const decoder = new TextDecoder('utf8');
   return decoder.decode(base64ToBuffer(str));
 }
+
+export const SOME_I18N_STRING = sprintf(__('this is a %{testStr}'), { testStr: 'test' });

2. Run the user_toggles_whitespace_changes_spec file

$ rspec ./spec/features/merge_request/user_toggles_whitespace_changes_spec.rb

3. The test will fail with a window is undefined error message.

MR acceptance checklist

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• I have evaluated the MR acceptance checklist for this MR.