Implement CIP12 to Yoroi backends

The Cardano Improvement Proposal number 12 defines on-chain stake pool operator to delegates communication.

To take advantage of this CIP, communication method needs to be implemented in Yoroi backend software, so that Yoroi and other lighweight wallet can make use of it.

We will implement and propose an enhancement to Yoroi backend software that will create a new endpoint that could be used to query all communication methods defined in CIP12.

https://github.com/cardano-foundation/CIPs/blob/master/CIP-0012/CIP-0012.md

We know this project doesn't completely fit within the developer ecosystem challenge. Still, we think that improving the stake pool operators communication with delegates is critical prior to the upcoming k and a0 changes would benefit everyone.

https://iohk.io/en/blog/posts/2021/03/04/not-long-till-d-0-day/

Please note, this proposal has been accepted in Fund 3, but ended up being over budget.

## Deliverables
We will implement and propose a change to Yoroi backends, introducing a new endpoint that will enable wallet developers to:

• Fetch the CIP12 defined message board communication of a specific stake pool
• Fetch the CIP12 defined direct delegate communication, filtered by specific stake pool and specific delegate's stake address

We will deliver these features within one month from receiving the budget.

## Relevant experience

We are co-authors of CIP 12.

Five Binaries is an infrastructure development company. We're Cardano pioneers - with the first Cardano block minted on an aeroplane, first stake pool on the ITN and the first Shelley transaction on the mainnet.

We are trusted by customers such as Emurgo, Trezor or Cardano Foundation. To get in touch or find more information about us, please visit https://fivebinaries.com/.

## Budget
We estimate it will take us 8 engineering-hours to complete the deliverables.

Our rate, which comprises of our engineers' salaries, infrastructure costs, office rent, accounting and taxes is 100 EUR per hour.

We pay our people well, because they are both skilled and exceptionally experienced in the industry. And last but not least, because we respect them and want them to feel good and appreciated while working on Cardano.