docs: Recommend to use log client

[oscard0m]

I would not use it, it increases the bundle size, and I want @octokit/webhooks to work well in contraint environments such as browsers and Cloudflare Workers in future.

We can recommend to use it to users as we do in @octokit/core: https://github.com/octokit/core.js#logging

Originally posted by @gr2m in #201 (comment)

[wolfy1339]

There is the log property in the options object arg of the Webhooks constructor.
It is documented in the README.
The middleware that was there at the time of this issue has been deprecated, and will be removed in v9

[github-actions]

🎉 This issue has been resolved in version 9.0.0 🎉

The release is available on:

• GitHub release
• npm package (@latest dist-tag)

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