create-svelte: Do not gitignore .env.example (fix #2925)

[gtm-nayan]

Fixes #2925, reason behind the proposed change stated there.

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Latest commit: 506ee5c

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create-svelte	Patch

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[benmccann]

this is how svelte.dev is setup: https://github.com/sveltejs/svelte/blob/master/site/.env.example