layouts: Support linking source in image captions

Doesn't break (previous) entries without "source", you can't tell
they're just empty, zero-space paragraphs.

Also minor CSS improvements in multi-line captions.

Signed-off-by: Eileen Yoon <[email protected]>

Author: eiln

layouts/shortcodes/captioned.html

@@ -1,3 +1,6 @@
 <figure class="captioned">{{ .Inner }}
-{{ with .Get "caption"}}<figcaption><p>{{.}}</p></figcaption>{{end}}
+<figcaption>
+    {{ with .Get "caption"}}<p>{{.}}</p>{{end}}
+    {{ with .Get "link"}}<p><a href={{.}}>{{end}}{{ with .Get "source"}}Source: {{.}}</a>{{end}}</p>
+</figcaption>
 </figure>

static/css/main.css

@@ -981,6 +981,8 @@ p img, figure img {
     padding-top: 10px;
     max-width: 100%;
     height: auto;
+    margin-top: 15px;
+    margin-bottom: 10px;
 }
 
 .center {
@@ -994,13 +996,17 @@ p img, figure img {
 }
 
 .post figure figcaption p {
-    margin-top: 10px;
-    margin-bottom: 10px;
+    margin: 0;
     text-align: center;
     font-weight: 300;
     font-size: 80%;
 }
 
+.post figure {
+    margin-top: 20px;
+    margin-bottom: 20px;
+}
+
 /* Blog */
 
 .blog-header {