[Fix] fix broken story in Prompt Custom Actions

[rshen91]

Summary

This is actually an issue with Storybook not with the component. storybookjs/storybook#11554

This PR updates the README.mdx with a proper example and fixes the story because of storybook's limitation.

In reviewing a PR I saw that the packages/shared-ux/prompt/not_found/src/not_found_prompt.stories.tsx story for CustomActions was broken. It was passing in an array leading to the below error:

This PR also shows the customization of the title and body prop added in PR #149924

Checklist

• Documentation was added for features that require explanation or tutorials

[rshen91]

This is a storybook issue in not being able to read the values of the array. I added the test to confirm that the component does render as expected.

[majagrubic]

Code review only, changes seem straightforward.

[kibana-ci]

💚 Build Succeeded

• Buildkite Build
• Commit: aced671
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Metrics [docs]

✅ unchanged

History

• 💚 Build #104760 succeeded bfd6213
• 💚 Build #104424 succeeded 5b142d9

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