verticalLetters property

@override String get verticalLetters

On the soft keyboard, some Mongol keys display vertical letters. So we need to set these letters in this variable.

Implementation

@override
String get verticalLetters => 'ᡐᡑᡕᡖ᠁ᡓᡒ᠄ᡝᡞ{}ᡣ~ᡛᡜᡗᡘᡙᡚ᠂᠃ᡥᡨ\nᡥᡧ';