Support kitty extended input mode in Free Vision

Some terminals, like kitty (https://sw.kovidgoyal.net/kitty/keyboard-protocol/), support extended input mode that gives more information about pressed keys. It would be extremely useful if Free Vision also supports it.

This feature is supported in modern Turbo Vision version for C++, it can be used as reference implementation: https://github.com/magiblot/tvision Relevant commit: https://github.com/magiblot/tvision/commit/6e5a7b46c6634079feb2ac98f0b890bbed59f1ba