Create an ERC721 smart contract

Update of the previous version that you can find here : https://github.com/0xNekr/HowToCreateERC721SC_v1

Creation of a basic ERC721 contract that allows :

Previous version

• A supply (number of NFT) of 100.
• A price of 0.00001 ether.
• Return to IPFS metadata.
• Allows to mint several NFTs at once.
• Allows to withdraw money from the smart contract by the owner.

New features

• Adding sales steps.
• Add a whitelist before the public sale.
• A whitelist price of 0.005 ether.
• A public price of 0.01 ether.
• Un arbre de merkle pour éviter de payer trop de frais de gas en whitelist.