Recommend onError() handler for renderFrames() in docs #500

The SSR documentation for https://remotion.dev/docs/ssr (and maybe other places in the docs), especially renderFrames() and renderStill() doesn't always use the onError() property, which leads to errors being swallowed.

🎃 This issue is eligible for Hacktoberfest! In addition to helping you get a contribution towards your Hacktoberfest reward, Remotion pays a $100 bounty for it!

Read: How to contribute to Remotion

• Let us know when you are interested in this issue, and we'll assign you!
• In order to prevent issues from getting stuck, try to progress the issue by opening a PR and adding commits. If your progress is stale for 7 days, another user can ask to take over the issue.

Approval criteria for this issue:

• Ensure the SSR page, and if there are other places where the docs don't use onError(), get updated.