Adds a live docs example for a Spanish translation for the custom file input to test out #23612 (closed). The CSS for this isn't included in v4 by default—instead, it's in our docs CSS. In my testing, the translation works as intended. Similarly, setting a custom lang attribute on the <input> doesn't break the English default from our source Sass (meaning any additional languages from the $custom-file-text Sass map will function correctly).
This should close #23612 (closed) without any actual fix being implemented.