Update IEthereumSignerCompatibleWithEthersV5

Extends the `Signer` interface from ethers v6 to include more methods
required by ethers v5.

sdk/src/lib/utils/ethereum-signer.ts

@@ -1,10 +1,10 @@
-import { VoidSigner as EthersVoidSigner } from "ethers"
+import { VoidSigner as EthersVoidSigner, Signer } from "ethers"
 
 /**
  * This abstract signer interface that defines necessary methods to be
  * compatible with ethers v5 signer which is used in tBTC-v2.ts SDK.
  */
-export interface IEthereumSignerCompatibleWithEthersV5 {
+export interface IEthereumSignerCompatibleWithEthersV5 extends Signer {
   /**
    * @dev Required by ethers v5.
    */

sdk/test/modules/tbtc/Tbtc.test.ts

@@ -4,7 +4,8 @@ import {
   Deposit as TbtcSdkDeposit,
 } from "@keep-network/tbtc-v2.ts"
 
-import { IEthereumSignerCompatibleWithEthersV5 } from "../../../src"
+import { ZeroAddress, Provider } from "ethers"
+import { IEthereumSignerCompatibleWithEthersV5, VoidSigner } from "../../../src"
 import Deposit from "../../../src/modules/tbtc/Deposit"
 import TbtcApi from "../../../src/lib/api/TbtcApi"
 
@@ -24,9 +25,11 @@ jest.mock("@keep-network/tbtc-v2.ts", (): object => ({
   ...jest.requireActual("@keep-network/tbtc-v2.ts"),
 }))
 
-class MockEthereumSignerCompatibleWithEthersV5
-  implements IEthereumSignerCompatibleWithEthersV5
-{
+class MockEthereumSignerCompatibleWithEthersV5 extends VoidSigner {
+  constructor() {
+    super(ZeroAddress, {} as Provider)
+  }
+
   getAddress = jest.fn()
 
   connect = jest.fn()