Production: Implement better factor contract pattern

[freelerobot]

Problem: the plugin references a single, static, nonchangeable smart contract address.

But each DF game is a new smart contract address, and our plugin depends on the respective DF contract addresses.

Potential solutions:

• Create a Nightmarket global factory contract which spins out a new Nightmarket contract for each new DF game contract. Enable this feature in game. A bit frictioned since one player will have to deploy new nightmarket contracts for each game.
• Rewrite Nightmarket contracts to work with all Darkforest games. It queries any address. The plugin instantiates the NightMarket contract with the DF contract address used for mappings/data lookups. Not super elegant, potential security issues.
• Open to potential, better solutions, I haven't thought about this too deeply.

[freelerobot]

const Greeter = await ethers.getContractFactory("Greeter");
already providedd by ethers... so easy

[dmpierre]

For now, a nightmarket factory contract has been implemented. See contracts/NightMarketFactory.sol