fix: import xhr2 to avoid reference error (#101)

[tkt9k2562]

Original Issue:
#101

[tkt9k2562]

I test it manually , by replacing the build/dicomweb-client.js which is generated after npm run build , and it works.

[pieper]

What does this do on a browser? Is it transparent and workable in node and browser or do we need to detect?

@wayfarer3130 @sedghi do you have any thoughts on this PR?

[wayfarer3130]

I don't know that it is going to work in a browser - that is something which would have to be tested to see what it does. One could export a method that just choose that import versus the browser version depending on if in node or the browser.

[pieper]

Thanks for the doublecheck @wayfarer3130 .

@tkt9k2562 can you look into making sure this works the same in node and the browser? Ideally with automated testing.

[sedghi]

I don't think this is the way, not sure what we need from xhr request but we can do something simpler like

let fetch;
if (typeof window === 'undefined') {
    fetch = await import('node-fetch').then(mod => mod.default);
} else {
    fetch = window.fetch; // Use browser's native fetch
}

or the solution above but dynamically choosing/importing that package instead of forcing it at import level