templates: add cover image to be linked into meta

for opengraph, schema and twitter

layouts/partials/templates/opengraph.html

@@ -2,6 +2,13 @@
 <meta property="og:description" content="{{ with .Description }}{{ . }}{{ else }}{{if .IsPage}}{{ .Summary }}{{ else }}{{ with .Site.Params.description }}{{ . }}{{ end }}{{ end }}{{ end }}" />
 <meta property="og:type" content="{{ if .IsPage }}article{{ else }}website{{ end }}" />
 <meta property="og:url" content="{{ .Permalink }}" />
+{{- if .Params.cover.image -}}
+{{- if (ne .Params.cover.relative true) }}
+<meta property="og:image" content="{{ .Params.cover.image | absURL }}" />
+{{- else}}
+<meta property="og:image" content="{{ (path.Join .RelPermalink .Params.cover.image ) | absURL }}" />
+{{- end}}
+{{- end }}
 {{ with $.Params.images }}{{ range first 6 . -}}
 <meta property="og:image" content="{{ . | absURL }}" />
 {{ end }}{{ else -}}

layouts/partials/templates/schema.html

@@ -5,6 +5,13 @@
 <meta itemprop="datePublished" {{ .PublishDate.Format $ISO8601 | printf "content=%q" | safeHTMLAttr }} />{{ end }}
 {{ if not .Lastmod.IsZero }}<meta itemprop="dateModified" {{ .Lastmod.Format $ISO8601 | printf "content=%q" | safeHTMLAttr }} />{{ end }}
 <meta itemprop="wordCount" content="{{ .WordCount }}">
+{{- if .Params.cover.image -}}
+{{- if (ne .Params.cover.relative true) }}
+<meta itemprop="image" content="{{ .Params.cover.image | absURL }}" />
+{{- else}}
+<meta itemprop="image" content="{{ (path.Join .RelPermalink .Params.cover.image ) | absURL }}" />
+{{- end}}
+{{- end }}
 {{ with $.Params.images }}{{ range first 6 . -}}
 <meta itemprop="image" content="{{ . | absURL }}">
 {{ end }}{{ else -}}

layouts/partials/templates/twitter_cards.html

@@ -1,3 +1,11 @@
+{{- if .Params.cover.image -}}
+<meta name="twitter:card" content="summary_large_image" />
+{{- if (ne $.Params.cover.relative true) }}
+<meta name="twitter:image" content="{{ .Params.cover.image | absURL }}" />
+{{- else }}
+<meta name="twitter:image" content="{{ (path.Join .RelPermalink .Params.cover.image ) | absURL }}" />
+{{- end}}
+{{ end }}
 {{- with $.Params.images -}}
 <meta name="twitter:card" content="summary_large_image"/>
 <meta name="twitter:image" content="{{ index . 0 | absURL }}"/>