image: support iterm2 image protocol

[jeffglover]

I really appreciate how streamlined kitty image protocol support is working over tmux + ghostty. As a user of rio terminal, iterm2 image protocol would fill that gap. Of course, iterm2 users would appreciate it as well.

The rio developer does have plans to implement kitty protocol in the future.

[kylesnowschwartz]

Big +1 ! As an iterm2 user I've found it weirdly difficult to get in-buffer images to 'just work' with neovim. See: 3rd/image.nvim#315

Having iterm2 image protocol support in snacks would be amazing. Thanks for your hard work Mr. Folke!