…s` (remix-run#184) (remix-run#2944)

Improves support for returned links that include an `imagesrcset` attribute to
preload images when matched against a responsive set of URLs. This only works
when `rel === 'preload'` and `as === 'image'`.
https://html.spec.whatwg.org/commit-snapshots/cb4f5ff75de5f4cbd7013c4abad02f21c77d4d1c/#attr-link-imagesrcset

Prior to this change, a few problems with our implementation:

1. Our types for `HtmlLinkDescriptor` make `href` required. This is true
   _unless_ a link includes `imagesrcset` and `imagesizes`, though `imagesrcset`
   and `href` will also work with or without `imagesizes` according to the spec.
   This change uses an intersection type to account for these cases.
2. React 17 was released prior to these attributes being accepted into the spec
   and implemented by browsers, so passing the props as camel-cased will issue a
   warning about unsupported DOM props. Our types recognized this and supported
   the all-lowercase version to skip the warning and forward the attribute to
   the node, but React 18 now recognizes the camel-cased version. This change
   updates our types to use the camel-cased prop names, but it will support
   either at runtime and normalize the object based on the detected version of
   React.
3. Because we use `href` + `rel` as a key, links without an `href` will have
   duplicate keys. So `imageSrcSet` is added as a fallback to prevent that.