Implement collapsing consecutive posts in a series

Signed-off-by: Danila Fedorin <danila.fedorin@gmail.com>

layouts/partials/post.html

@@ -15,4 +15,13 @@
     </p>
     {{ end }}
     <p class="post-preview">{{ .page.Summary }} {{ if .page.Truncated }}...{{ end }}</p>
+    {{- if .linkSeries -}}
+    {{- $term := index (.page.GetTerms "series") 0 -}}
+    {{- with $term -}}
+    <p class="series-link">
+    {{- partial "icon.html" "corner-down-right" -}}
+    {{- i18n "latestInSeries" }} <a href="{{ $term.Permalink }}">{{ $term.Title }}</a>
+    </p>
+    {{- end -}}
+    {{- end }}
 </li>