Add support for changing text alignment

Browsers like Firefox and Chromium (on Windows) have support for temporarily change text alignment of text boxes, typically by press RCtrl+RShift or LCtrl+LShift or by Ctrl+Shift+X to toggle alignment on Firefox Linux.

This feature (toggling RTL, LTR directions) is essential for Bidi support.

To clarify, this is not the same as setting attribute `direction="rtl";` in `<form>` tag. It only changes the direction "temporarily" for the user.