fix: add ethers types to contracts-node and contracts-frontend

[mrice32]

Motivation

Importing ethers event types from contracts-node doesn't work.

Summary

You can now import ethers event types by doing the following:

import { MyContractEthersTypes } from "@uma/contracts-node";

const myVar: MyContractEthersTypes.SomeEvent = ...

Testing

Check a box to describe how you tested these changes and list the steps for reviewers to test.

• Ran end-to-end test, running the code as in production
• New unit tests created
• Existing tests adequate, no new tests required
• All existing tests pass
• Untested

Issue(s)

N/A

[md0x]

This fix would be useful!

This is how I was importing event types:
https://github.com/UMAprotocol/protocol/blob/master/packages/monitor-v2/src/monitor-polymarket/MonitorProposalsOrderBook.ts#L2

Do we want to add this changes @mrice32 ?