Incentivize requests from hyperbridge

[seunlanlege]

When dispatching a few requests from hyperbridge, we should attach a reward in the native token to incentive relayers to facilitate their delivery & execution.

eg

• System cross-chain messages

pallet-relayer will need to be updated to accept proofs of delivery of hyperbridge-originated requests.

[seunlanlege]

I think we can use pallet-relayer for this. It should award BRIDGE tokens to relayers who prove that they delivered a request that originated from Hyperbridge.

Also the messaging task in the relayer should submit proofs of messages delivered from hyperbridge to pallet-relayer to claim rewards