`src` does not reflect `basePath` for statically-imported images

[srmagura]

Next allows you to configure a basePath so you can serve your site from a subpath. For example, we deploy our Next.js site to www.spotvirtual.com/_preview so we can test changes before making them live at www.spotvirtual.com.

I noticed that the generateImageURL code from ExportedImage.tsx does not take basePath into account for statically-imported images. Ideally, it would prepend the basePath since this is what next/image does.

It should be easy to fix. I may send a PR for this, though I am leaning towards changing our deployment so that the preview site is served from a different subdomain, e.g. www-preview.spotvirtual.com. This would prevent issues like this from arising in the first place.

There is a related next.config.js property called assetPrefix. Ideally the PR for this would take assetPrefix into account too. If both basePath and assetPrefix are set, I'm not sure which one "wins".