Update Development environment setup in readme

[luu-alex]

Overview

Environment:
node v18
macOS

I was cloning the repo and was trying to run testcases but trying to run npm install leads to an npm error:

npm ERR! code EUNSUPPORTEDPROTOCOL
npm ERR! Unsupported URL Type "workspace:": workspace:*

This issue can be solved with pnpm. pnpm needs to be installed first and must use pnpm install
Unless i missed a step, the readme should be updated so that this issue can be avoided :)

Steps to reproduce

➜  deletesoon git clone https://github.com/solana-labs/solana-web3.js.git
Cloning into 'solana-web3.js'...
remote: Enumerating objects: 175662, done.
remote: Counting objects: 100% (36286/36286), done.
remote: Compressing objects: 100% (1299/1299), done.
remote: Total 175662 (delta 35360), reused 35673 (delta 34970), pack-reused 139376
Receiving objects: 100% (175662/175662), 94.07 MiB | 10.33 MiB/s, done.
Resolving deltas: 100% (164190/164190), done.
➜  deletesoon ls
solana-web3.js
➜  deletesoon cd solana-web3.js 
➜  solana-web3.js git:(master) ls
CONTRIBUTING.md     LICENSE             README.md           SECURITY.md         commitlint.sh       package.json        packages            pnpm-lock.yaml      pnpm-workspace.yaml scripts             turbo.json
➜  solana-web3.js git:(master) npm install
npm ERR! code EUNSUPPORTEDPROTOCOL
npm ERR! Unsupported URL Type "workspace:": workspace:*

npm ERR! A complete log of this run can be found in: /Users/alexluu/.npm/_logs/2024-03-16T19_10_45_000Z-debug-0.log

Description of bug

[github-actions]

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