Add security headers

[jwm0]

I want to merge this change because...

Screenshots

Pull Request Checklist

1. [ ] All visible strings are translated with proper context.
2. [ ] All data-formatting is locale-aware (dates, numbers, and so on).
3. [ ] The changes are tested.
4. [ ] The code is documented (docstrings, project documentation).
5. [ ] Changes are mentioned in the changelog.

Test Environment Config

API_URI=https://qa.staging.saleor.cloud/graphql/

[patrys]

Task linked: SALEOR-4293 Add security headers to vercel deployments

[vercel[bot]]

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storefront-master-staging – ./

🔍 Inspect: https://vercel.com/saleorcommerce/storefront-master-staging/5D89rEUs5coXcUzixpdHQhzqRQXb
✅ Preview: https://storefront-master-staging-git-saleor-4293-ad2abe-saleorcommerce.vercel.app

storefront-qa – ./

🔍 Inspect: https://vercel.com/saleorcommerce/storefront-qa/3DFQtreZepaEJFfX12htsVQBAJf3
✅ Preview: https://storefront-qa-git-saleor-4293-add-securit-8ad215-saleorcommerce.vercel.app

storefront-stable-staging – ./

🔍 Inspect: https://vercel.com/saleorcommerce/storefront-stable-staging/7bFAHfAZyErwyXCNtX2b489FpA5W
✅ Preview: https://storefront-stable-staging-git-saleor-4293-ebfe84-saleorcommerce.vercel.app

internal-demo-storefront – ./

🔍 Inspect: https://vercel.com/saleorcommerce/internal-demo-storefront/6gb2XAitbaXSNAiqcPfnQf5hWdh9
✅ Preview: https://internal-demo-storefront-git-saleor-4293-9fe1d8-saleorcommerce.vercel.app

storefront-demo – ./

🔍 Inspect: https://vercel.com/saleorcommerce/storefront-demo/13XmaXeBkvMUWwADvjjdLARbQHak
✅ Preview: https://storefront-demo-git-saleor-4293-add-secur-26590d-saleorcommerce.vercel.app