Dutch Auction

[AnmolSirola]

Description

Seller of NFT deploys this contract, participants can bid by depositing ETH greater than the current highest bidder. All bidders can withdraw their bid if it is not the current highest bid. Also the auction lasts for 7 days.

Fixes #115

Screenshots of relevant screens

Developer's checklist

• [x] My PR follows the style guidelines of this project
• [x] I have performed a self-check on my work
• [x] I have followed the coding guidelines
• [x] My changes in code generate no new warnings
• [x] I have added relevant screenshots in my PR