Support kitty `Virtual Placement` / `Unicode placeholders` extension

[hasezoey]

I have just recently become aware that kitty got a extension for virtual placements via Unicode placeholers.
Kitty Graphics Protocol: Unicode placeholders

If i understand this extension correctly, this allows location (and maybe size) of images to be controlled by unicode characters that can be printed like normal, the terminal will fit it there. They can also be moved without having to send another kitty protocol command.