fix: support images array for featured image (#967)

Patrick Kollitsch

yesterday ad433679f34ff636f07026d42b21ffeb3dd54e97

fix: support images array for featured image (#967)

## Summary

* Adds `Params.images` fallback support to
`layouts/_partials/func/GetFeaturedImage.html`.
* Keeps `featured_image` as the primary source for backwards
compatibility.
* Uses the first value from `images` when `featured_image` is not set,
matching Hugo's embedded-template image metadata convention.
* Preserves existing Page Resource resolution for exact matches and the
existing `cover`/`feature` page-resource fallback.

## Issue

Closes #77.

## Documentation

Documentation PR: gohugo-ananke/documentation#10

## Verification

* Inspected issue #77 and its comments.
* Checked repository contribution guidance in `CONTRIBUTING.md`.
* Reviewed the existing featured image helper before changing it.
* No local Hugo build was run because the execution container cannot
resolve `github.com` for cloning dependencies.

## Notes

The lookup order after this change is:

1. `featured_image`
2. First value in `images`
3. First page resource containing `feature` or `cover` in its path

 layouts/_partials/func/GetFeaturedImage.html

@@ -5,11 +5,14 @@

    If a featured_image was set in the page's front matter, then that will be used.

    If no featured_image was set, this will use the first image from the page's
    images front matter array.

    If not set, this will search page resources to find an image that contains the word
    "cover", and if found, returns the path to that resource.

    If no featured_image was set, and there's no "cover" image in page resources, then
    this partial returns an empty string (which evaluates to false).
    If no featured_image or images value was set, and there's no "cover" image in page
    resources, then this partial returns an empty string (which evaluates to false).

    @return RelPermalink to featured image, or an empty string if not found.

@@ -27,11 +30,24 @@
  {{ with $.Resources.GetMatch . }}
    {{ $linkToCover = .RelPermalink }}
  {{ end }}
{{/* Find the first image with 'cover' in the name in this page bundle. */}}
{{ else }}
  {{ with .Resources.ByType "image" }}
    {{ with .GetMatch (fmt.Printf "**{%s}*" $matches) }}
      {{ $linkToCover = .RelPermalink }}
  {{/* Use the first value from the images front matter array if present. */}}
  {{ with .Params.images }}
    {{ range first 1 . }}
      {{ with . }}
        {{ $linkToCover = strings.Trim . "/" | urls.AbsURL }}
        {{/* If we find a Page Resource matching the exact value, we use it instead. */}}
        {{ with $.Resources.GetMatch . }}
          {{ $linkToCover = .RelPermalink }}
        {{ end }}
      {{ end }}
    {{ end }}
  {{/* Find the first image with 'cover' in the name in this page bundle. */}}
  {{ else }}
    {{ with .Resources.ByType "image" }}
      {{ with .GetMatch (fmt.Printf "**{%s}*" $matches) }}
        {{ $linkToCover = .RelPermalink }}
      {{ end }}
    {{ end }}
  {{ end }}
{{ end }}