Add fishermen section

[ansonla3]

-What's the role of fishermen responsible for?

-Mechanism of the whole reporting procedure

-Which level of the slashing(4 different levels) will be specifically for fishermen

-Is that anyone allows being a fisherman (just by running a program)?
-Required to lockup DOT or not?
Only allow validators to run or open for everyone (I think it makes sense to open for anyone with depositing a minimums amount of DOT for security purpose to prevent misbehaviour in the network(e.g. keep submitting incorrect reports)

-Rewards mechanism
the first reporter gets all or based on the submission time or case by case?

-Fishermen program
Running an external fishermen program (e.g. MakerDAO CDP keeper) or could be a Polkadot node with customised configuration?