docs: Add example config "template" for various levels of activity

[carlaKC]

A pre-defined config with various levels of activity already built in was much-requested on user calls.

MVP:

• Check in an example_config.json that has empty fields for node details (we can't pre-set this) and various different types of activity specified (high/low frequency, high/low amount etc).

We could extend this further to have different "profiles" like:

• sink: one node receives a lot of payments from the network
• source: one node sends a lot of payments to various destinations
• popular: one pair on nodes send/receive a high amount of traffic between themselves

[zealsham]

Is this still a valid issue and something we are willing to do ? . we already have an example config file but not explicitly seperated into sink, source and popular.

[carlaKC]

This still isn't very high priority for me personally, since nobody has showed up on the issue asking for this.