post-cover: add support for adding caption (#17)

* shown only on single page

usage =>
in page-vars front-matter

cover:
  image: '<image path/url>'
  alt: '<alt text>'
  caption: '<text>'

assets/css/post-entry.css

@@ -88,9 +88,15 @@
     font-size: 14px;
 }
 
+.entry-cover {
+    margin-bottom: var(--gap);
+    text-align: center;
+    font-size: 14px;
+    color: var(--secondary);
+}
+
 .entry-cover img {
     border-radius: var(--radius);
-    margin-bottom: var(--gap);
     pointer-events: none;
     width: 100%;
 }

layouts/_default/single.html

@@ -33,6 +33,7 @@
     {{- else}}
     <img src="{{ .Permalink -}} {{- .Params.cover.image }}" alt="{{ .Params.cover.alt | plainify }}">
     {{- end}}
+    <p>{{.Params.cover.caption}}</p>
   </figure>
   {{- end }}
   {{- if .Params.ShowToc }}