[Documentation] add some information and simple examples (scripts) about how to receive messages and attachments

[Wikinaut]

Proposal (and I offer to help here) to add some lines of text how messages and attachments are received → would be helpful.

I managed to install signal-cli and run it as a systemd service, and also used the receive.py to see everything working and received also attachments to /var/lib/signal-cli/attachments directory. Of course, journalctl -f -u signal-cli lists the received messages as well.

However, in my view as a beginner to the wonderful (and sometimes weird) world of signal-cli, it would be nice to have some basic information (or methods inside signal-cli), how received messages and attachments could be automatically stored and logged into for example mbox-like structures, or using the -o json format or to trigger some other useful things on the server.

I saw for example the signal-to-mail gateway, but one or two smaller examples would be perhaps helpful, too.

What are your thoughts?

And, by the way, the https://github.com/AsamK/signal-cli/blob/master/man/signal-cli.1.adoc page should be linked from the (present) Wiki Home page.