Restore terminal title

[avlapp]

First, impressive work!

On Linux using Bash:

This changes the terminal title:
// Change a terminal title.
if is_tmux {
os.Stdout.WriteString("\033kgoful\033") // for tmux
} else {
os.Stdout.WriteString("\033]0;goful\007") // for otherwise
}

But closing Goful doesn't restore the terminal title.