Fix the edge function crash on Vercel

[marcomontalbano]

What I did

Use btoa and atob directly without checking globalThis nor window.

Before this fix the edge function was crashing on Vercel:

TypeError: Illegal invocation
    at (../src/utils/base64.ts:41:22)
    at (../src/jwtDecode.ts:18:23)
    at (../src/jwtVerify.ts:14:31)
    at (src/middlewares/withCommerceLayer.ts:15:31)
    at (node_modules/.pnpm/next@14.2.5_react-dom@18.3.1_react@18.3.1__react@18.3.1/node_modules/next/dist/esm/server/web/adapter.js:158:0)

I also added a Next.js example deployed on Vercel and Netlify.

How to test

This example is now working as expected: https://commercelayer-js-auth-nextjs.vercel.app/middleware

Checklist

• Make sure your changes are tested (stories and/or unit, integration, or end-to-end tests).
• Make sure to add/update documentation regarding your changes.
• You are NOT deprecating/removing a feature.

[vercel]

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Name	Status	Preview	Comments	Updated (UTC)
commercelayer-js-auth-nextjs	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Jul 12, 2024 2:25pm

[netlify]

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[acasazza]

Well done