Add helper classes to docs

[aliabd]

Adds helper classes to docs: Brush and Eraser to Image Editor, and WaveformOptions to Audio. Also links to them from the kwarg descriptions.

Closes: #8492

[gradio-pr-bot]

🪼 branch checks and previews

•	Name	Status	URL
	Spaces	ready!	Spaces preview
	Website	ready!	Website preview
	Storybook	ready!	Storybook preview
🦄	Changes	detected!	Details

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Install Gradio from this PR

pip install https://gradio-builds.s3.amazonaws.com/142e1c28ed325764eed09e5c1079c66e89a31828/gradio-4.36.1-py3-none-any.whl

Install Gradio Python Client from this PR

pip install "gradio-client @ git+https://github.com/gradio-app/gradio@142e1c28ed325764eed09e5c1079c66e89a31828#subdirectory=client/python"

Install Gradio JS Client from this PR

npm install https://gradio-builds.s3.amazonaws.com/142e1c28ed325764eed09e5c1079c66e89a31828/gradio-client-1.1.1.tgz

[gradio-pr-bot]

🦄 change detected

This Pull Request includes changes to the following packages.

Package	Version
gradio	patch
gradio_client	patch
website	patch

• Maintainers can select this checkbox to manually select packages to update.

With the following changelog entry.

Add helper classes to docs

Maintainers or the PR author can modify the PR title to modify this entry.

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• Maintainers can change the version label to modify the version bump.
• If the bot has failed to detect any changes, or if this pull request needs to update multiple packages to different versions or requires a more comprehensive changelog entry, maintainers can update the changelog file directly.

[pngwn]

Perfect! Thanks @aliabd!