chore: update the javascript sdk for zksync era documentation

[Ngozi-Txfusion]

What

• Update the troubleshooting page to remove Bun.
• Update the ethers-v6 providers with the complete content.
• Write a Quickstart guide for new users of JavaScript ethers.

Why

• Sabrina requested the Bun section be removed as ZKsync does not maintain Bun.
• Updating the ethers-v6 providers ensures that users can access complete and accurate information, improving their development experience.
• A Quickstart guide is essential for new users to quickly get up to speed with JavaScript ethers, providing them with a seamless onboarding experience.

[github-actions]

Visit the preview URL for this PR (updated for commit ed47697):

https://zksync-sdk-docs-staging--pr52-update-the-javascrip-t0x4wius.web.app

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