Add option to specify remote domains for image resizing

[paulrobertlloyd]

Fixes #814.

Currently the image resizing plugin only supports resizing remote images saved to the destination publication URL (publication.me). However, it’s possible to configure Indiekit such that files can be saved to other destinations, such as S3-compatible bucket storage.

This PR adds a domains option which gets passed to the same option on ipxHttpStorage() which controls which remote URLs image resizing is allowed for.

For example, if your website is at https://website.example, but media files are saved to https://media.example, you could use the following configuration options:

{
  publication: {
    me: "https://website.example"
  },
  ["@indiekit/endpoint-image"]: {
    domains: ["https://media.example"]
  }
}

[eclecticpassions]

I will test this out and report back, thank you for adding this feature/option!

Edit: I don't know how to test this out, do I have to be on ^1.0.0-beta.26 for @indiekit/indiekit?

The PR mentions setting a https://media.example domain for endpoint-image used in resizing only (which will solve the image thumbnail fail). But does it mean I can use an absoluteURL for media: {url: "https://cdn-to-bucket.com/content/photos/{yyyy}/{DDD}{n}.{ext}"} instead of a relativeURL with the CDN "Override Origin URL" workaround?