Nightshade consensus

NEAR is using "Nightshade" consensus algorithm, which is a BFT-based algorithm. Additionally, the mechanism to prevent Sybil attack and provide election of validators for the consensus is done via "Thresholded Proof of Stake".

For more information, see the draft Nightshade spec at https://www.overleaf.com/read/snswgqkjvwvy‚Äč