Advanced Challenge Submission

[HashWarlock]

This is my advanced challenge submission. I did not finish implementation, but put code in a stable state before submission. I plan to work on this further past deadline as I want to utilize it for a ghost auction for my NFT collection.

README.md: https://github.com/HashWarlock/phala-ghost-auction/blob/off-chain-nft-auction/README.md
Ghost Auction phala-blockchain code: https://github.com/HashWarlock/phala-ghost-auction
Ghost Auction frontend: https://github.com/HashWarlock/js-sdk
Discord: hashwarlock#8457

Thank you for all the fun and new knowledge. I'm very excited to learn more and more as the days pass. Have a great day.