"Keep alive" option

[keynmol]

If you are investigating a server that is crashing (like I'm doing at this moment), it would be useful if Langoustine didn't shutdown with it.

Because we don't persist any data in memory on the client side, you immediately lose access to the logs/traces.

What I would like is

1. A --keep-alive CLI option for the trace command, that will not shutdown the tracer if the child process is shut down
2. A Keep alive toggle in the UI, which can enable the mode on an already running server (so you can enable it right before you perform an action that crashes your server)