Request: Add docs page about the `rippled` config file (`rippled.cfg`)

[intelliot]

In rippled 2.0.1, a new line in cfg/rippled-example.cfg sets the recommended send_queue_limit to 500.

There is no documentation of the send_queue_limit setting. Ideally, it would be documented somewhere on xrpl.org.

It could be a page specific to documenting the [server] stanza, or it could be a page that gives an overview and/or highlights of various parts of rippled.cfg overall. (I'm happy either way.)