Extending Unicode highlight to language mixture highlight

<!-- ⚠️⚠️ Do Not Delete This! feature_request_template ⚠️⚠️ --> <!-- Please read our Rules of Conduct: https://opensource.microsoft.com/codeofconduct/ --> <!-- Please search existing issues to avoid creating duplicates. --> <!-- Describe the feature you'd like. --> Unicode highlight feature is great if one uses only ASCII characters. I'd like to suggest a more general and natural feature: highlight any mixture of languages in strings. Cyrillic letter 'о' is wrong in word 'w**о**rk' as well as ASCII character 'o' in word 'м**o**локо'. So it would be great to have highlighting of any characters that are of different language in any characters sequence without separators and special symbols.