Fix: Handle storybook V8 fetch call

[bassem-i]

We are currently migrating our Storybook version from 7 to 8. We've noticed that:

A fetch call in Storybook V8 breaks loki's aws-lambda-renderer.

Storybook V8 initialization calls getStoryIndexFromServer function which tries to load a file called index.json (A json with all the stories loaded in the storybook build) using fetch. This breaks Loki's aws-lambda-renderer because it depends on file-based file://TMP_FOLDER/iframe.html?id=STORY_ID access. (File-based access doesn't support fetch).

This PR fixes the failed to fetch error by handling the fetch call without actually fetching.

1. Loki's aws-lambda-renderer script (running on lambda) does a readFileSync to load the content of index.json file.
2. Loki's aws-lambda-renderer script injects a script into the chrome tab running Storybook to overwrite the fetch function implementation as follows:

• If fetch is called with index.json, it returns the stories list.
• If fetch is called with any other input, it invokes the original fetch.

[bassem-i]

I've found another approach that keeps the file-based url access: #546