Fix typescript issue

#4

a plugin for using sourcify with hardhat

I just want to use sourcing but I don't want use it with hardhat-deploy (I don't deploy my contract with it) :/

So I created this plugin for using sourcing with hardhat. It submit the code to sourcify using the build file of harhat generated itself. so it should work for any hardhat project :D

rightnow it's a simple version works for single contract.

plan to improve it to:

1. simplify the inputs
2. support verify multiple contracts 

usage

task name sourcify is already used by hardhat-deploy :/

so I have to change to a new task name. may change to a simpler task name if i can come up with one :D

yarn hardhat sourcifySubmit --contract-name "Greeter" --source-name "contracts/Greeter.sol" --address 0xxxxxxxxx --chain-id 3

use yarn hardhat help sourcifySubmit to see the help for the task