Runtime agnostic - Support non-Node.js runtimes

[MickL]

This package is clearly named "-node" but I wonder if it uses Node specific imports or if it runs in other runtimes, too. E.g.:

• Bun
• Deno
• Serverless workers / Edge workers (Amazon Lambda, Cloudflare Workers, etc.)

What I would expect:

• If it is already platform agnostic, add this info to the readme/docs and rename the package e.g. mollie-api-javascript
• If it is not, try to make it work with web standards (e.g. use fetch) and treat Node specific behavior as an exception.

IMO all libraries should aim to be platform agnostic. E.g. Bun outperforms Node and sticks to web standards. Also serverless (edge) functions are a very common usecase in modern architecture. Especially Node has some quirks that are Node specific and not web standard, so personally I would treat Node more as an exception than the standard. E.g. an API developed with something like H3/Nitro runs/deploys "everywhere" but would then possibly fail using mollie-api-node.