Support IME input in masked password fields

Currently, entering Chinese characters in a password field requires enabling “Show password”. Pasting the same characters works even when the password is masked. This matches the behavior reported in #227.

Would it be feasible to enable IME input while keeping the password masked? One possible approach is to call ImmAssociateContextEx(hwnd, nullptr, IACE_DEFAULT) after setting the password character with EM_SETPASSWORDCHAR.

Are there any known compatibility concerns with this approach, or is disabling IME in masked password fields an intentional design choice?