Feat: support ethers v5 and v6 for ethers-ext

[Sotatek-TanHoang]

1. Add support for both ethers v5 and v6

2. about ethers v6 updates

   • ethers-ext sdk support for ethers v6
   • examples for ethers-ext with ethers v6
   • unit-tests for ethers-ext with ethers v6

3. Example usage of ethers-ext with ethers v5 and v6:

   • 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";