Simplify ra-data-localforage setup

[djhi]

Problem

Setting up the ra-data-local-forage dataProvider is cumbersome.
You have to manage a state and initialize it in a useEffect.

Solution

Simplify the setup.

• Implement the solution
• Showcase it in a story

How To Test

In storybook

https://react-admin-storybook-git-ra-data-localforage-s-a105c6-marmelab.vercel.app/?path=/story/ra-data-local-forage--basic

In a new app

• build the project
• create a new react-admin app using the fakerest dataprovider
• copy the ra-data-local-forage inside the new project node_modules
• Setup the dataProvider instead of fakerest

Additional Checks

• The PR targets master for a bugfix, or next for a feature
• The PR includes unit tests (if not possible, describe why)
• The PR includes one or several stories (if not possible, describe why)
• The documentation is up to date

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