Replace Axios with regular fetch

[Skaldebane]

In environments like Cloudflare Workers and Pages Functions, Axios requests don't work because XMLHttpRequests are not supported.

Replacing it with a regular fetch fixes this.

[CLAassistant]

All committers have signed the CLA.

[lukasIO]

Not against this change, but we have to keep in mind that fetch is only available in node without flags since v18.
For a v2, I guess we could also bump the minimum node requirement to v18. But we should make sure that other environments that we want to target, also support fetch ootb.

[davidzhao]

should we use something like node-fetch for node env?

[lukasIO]

IIRC there were some inconsistencies between native fetch and node-fetch last time I came across it.
Ideally we wouldn't need to include it.
I did a quick check for other popular JS runtimes and they all implement fetch ootb, so I guess we're fine as long as we bump nodeJS requirement to v18, which makes sense as everything else has reached EOL already.

[davidzhao]

Thanks @lukasIO, merging this.