feat: bump ShopifyCheckoutSheetKit dependency to 3.8.0

[kieran-osgood-shopify]

What changes are you making?

3.8.0 brings the Storefront API up to 2026-04

From the Swift PR Shopify/checkout-sheet-kit-swift#555:

Bump apiVersion to 2026-04
Add explicit handling for MERCHANDISE_LINE_TRANSFORMERS_RUN_ERROR error code (new in 2026-04) in both CartErrorCode and CartCompletionErrorCode — interrupts with .other reason to fall through to web checkout, matching portable-wallets behavior
Add GIFT_CARD_RECIPIENT_INVALID error code (new in 2026-01) to CartErrorCode — interrupts with .unhandled as gift cards are not applicable in the Apple Pay flow
No breaking changes affect the kit between 2025-10 and 2026-04.

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PR Checklist

Important

• I've added tests to support my implementation
• I have read and agree with the Contribution Guidelines.
• I have read and agree with the Code of Conduct.
• I've updated the README.

Releasing a new version of the kit?

• I have bumped the version number in the package.json file.

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Tip

See the Contributing documentation for instructions on how to publish a new version of the library.

[kieran-osgood-shopify]

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• feat: bump ShopifyCheckoutSheetKit dependency to 3.8.0 #464 👈 (View in Graphite)
• feat: bump ShopifyCheckoutSheetKit dependency to 3.7.0 #463
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