ssh kitten: Allow to configure HOME environment variable

Useful if the user does not have a home directory or the directory is
not writable.

shell-integration/ssh/bootstrap.sh

@@ -62,6 +62,8 @@ dcs_to_kitty() { printf "\033P@kitty-$1|%s\033\134" "$(printf "%s" "$2" | base64
 debug() { dcs_to_kitty "print" "debug: $1"; }
 echo_via_kitty() { dcs_to_kitty "echo" "$1"; }
 
+# If $HOME is configured set it here
+EXPORT_HOME_CMD
 # ensure $HOME is set
 [ -z "$HOME" ] && HOME=~
 # ensure $USER is set