add import and export

README.md

@@ -18,6 +18,7 @@ sudo terractl attach calamity
 - **A live console.** `terractl attach` shows the server's output and lets you type commands into it.
 - **Mod management.** `terractl mods` installs, enables and removes mods, with correct file ownership.
 - **Tab completion** for commands, instance names, mods and console commands.
+- **Export and import.** Pack an instance into one `.tar.gz` for backups or moving to another machine, and import it anywhere, with paths, ports and ownership adjusted.
 - **Hardened.** Servers run as an unprivileged `terraria` user and can only write to their own data.
 - **Helper for Windows.** A PowerShell script exports your enabled tModLoader mods for the server.