Implement Compact Sparse Merkle Tree (CSMT) in javascript/solidity

[eezcjkr]

Reference: https://github.com/ZanjeerPlatform/csmt

We should implement CSMT to allow for verifiable reads/writes to be done in NSTs.

Checklist:

• JavaScript library that implements the reference and can also generate proofs needed for reads, writes etc. in solidity
• Solidity library that keeps the root of CSMT and can verify reads (inclusion, non-inclusion) and writes (insertion, deletion)

[johannbarbie]

WHY?
Compact sparse merkle trees (CSMT) can implement authenticated mappings potentially more efficient than the Patricia Merkle Tree known in Ethereum. This opens the opportunity to outsource data storage off-chain and only keep the root of the authenticated data structure on chain. When read, add, update and delete operations are required, proofs are passed along with the transaction data to operate on the data without holding the data itself on-chain. This issue will create a pair of on/off-chain library that can be used in this way.