Add accessilbilty check and fixes

layouts/_markup/render-image.html

@@ -0,0 +1,30 @@
+{{- /*
+Content images. The Markdown title ("![alt](src "© Credit")") is the photo credit; it is shown
+as a caption instead of a tooltip, so that it is available on touch devices and to screen readers.
+An image on its own line becomes a figure; images sharing a paragraph get an inline credit.
+*/ -}}
+{{- $src := .Destination -}}
+{{- $width := 0 -}}
+{{- $height := 0 -}}
+{{- with or (.PageInner.Resources.Get (strings.TrimPrefix "./" .Destination)) (resources.Get .Destination) -}}
+  {{- $src = .RelPermalink -}}
+  {{- if and (eq .ResourceType "image") (ne .MediaType.SubType "svg") -}}
+    {{- $width = .Width -}}
+    {{- $height = .Height -}}
+  {{- end -}}
+{{- end -}}
+{{- /* A title that only repeats the alt text is not a credit. */ -}}
+{{- $credit := cond (eq .Title .PlainText) "" .Title -}}
+{{- $img := printf `<img src="%s" alt="%s"%s>` (htmlEscape $src) (htmlEscape .PlainText) (cond (gt $width 0) (printf ` width="%d" height="%d"` $width $height) "") -}}
+{{- if .IsBlock -}}
+<figure class="content-image">
+{{ $img | safeHTML }}
+{{- with $credit }}
+<figcaption class="content-image__credit">{{ . }}</figcaption>
+{{- end }}
+</figure>
+{{- else if $credit -}}
+<span class="content-image">{{ $img | safeHTML }}<span class="content-image__credit">{{ $credit }}</span></span>
+{{- else -}}
+{{ $img | safeHTML }}
+{{- end -}}