Feature request: add autossh like option

Hi!

I use `mssh` to create an SSH tunnel.
Something that I think could be interesting is to have an [autossh](https://www.everythingcli.org/ssh-tunnelling-for-fun-and-profit-autossh/) like option.
This would allow the SSH tunnel to be "persistent", meaning that the tunnel would always run. For example, once the ssh connection times out (By server-side timeout), the tunnel would be re-established automatically.

Thank you!

The issue identifies mssh and requests an autossh-like persistent tunnel; start by locating the CLI entry point and current SSH tunnel lifecycle. Define the reconnect and timeout behavior, then verify that a tunnel is re-established after a server-side timeout.

Written by the indexing model from the issue text.