ethers: Separate v5 and v6 subpaths

[blukat29]

Using with ethers v5

// commonjs
const { Wallet } = require("@klaytn/ethers-ext")
const { Wallet } = require("@klaytn/ethers-ext").v5
const { Wallet } = require("@klaytn/ethers-ext/v5")

// esm
import { Wallet } from "@klaytn/ethers-ext";

// esm
import { v5 } from "@klaytn/ethers-ext";
const { Wallet } = v5;

// esm subpath import. If using typescript, add "moduleResolution": "nodenext" to tsconfig.json
import { Wallet } from "@klaytn/ethers-ext/v5";

Using with ethers v6

// commonjs
const { Wallet } = require("@klaytn/ethers-ext").v6
const { Wallet } = require("@klaytn/ethers-ext/v6")

// esm
import { v6 } from "@klaytn/ethers-ext";
const { Wallet } = v6;

// esm subpath import. If using typescript, add "moduleResolution": "nodenext" to tsconfig.json
import { Wallet } from "@klaytn/ethers-ext/v6";

[blukat29]

Continued in #7