Add Synthetix ERC721 Staking Repo

optimize deleting item from array

added script for test

Merge pull request #5 from andreitoma8/version-zero-two

adding tests for withdrawal and claiming rewards

added tests for withdrawing and claiming rewards

add tests for staking

add extra step to goerli deployment

deleted old tests

updated readme

readability changes

added natspec contract description

added updateRewards function

changed `stakers[msg.sender]` to storage `staker`

store tokenIds staked by each user on-chain