fix: add redirects for routes containing '__data.json' suffix

[ericapisani]

Fixes #4872

We also needed to await the builder.createEntries call as it was not completing before the redirects array was being written to the build/redirects file.

Demo of site before fix: https://627c046d20bc620009be8eef--test-ssr-split.netlify.app/endpoint
Demo of site after fix: https://ep-svelte.netlify.app/

Way to reproduce/confirm fix

• Visit one of the above links
• Visit either 'endpoints' or 'todos' page

Before:

• Would see a 404 on both pages
• Refreshing on 'endpoints' page would render the page correctly, but not on todos
• Checking the network tab when navigating to todos through client side navigation showed that the route for todos/__data.json (and the related one for endpoints) was returning a 404

After:

• Correct page will render, both in client side navigation and when refreshing on the page itself

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🦋 Changeset detected

Latest commit: 74d63c3

The changes in this PR will be included in the next version bump.

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Name	Type
@sveltejs/adapter-netlify	Patch

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[nickytonline]

Thanks for the fix @erica. Looks great!

[Rich-Harris]

excellent, thanks so much!