Break section template into first and descendent sections

First section templates render the most recent $n yearly subsections as a list of
articles.

Descendent sections render just the content of those subsections.

layouts/partials/page/section_year_nav.html

@@ -0,0 +1,13 @@
+{{- $years := .years -}}
+{{- $includeCollapsedYearItem := .includeCollapsedYearItem -}}
+<nav class="year-nav  tag">
+  <span class="tag__name">{{ i18n "yearsTagTitle" }}</span>
+  <ul class="tag__value--list">
+    {{ range $years -}}
+      <li class="tag__value__list-item"><a href="#{{ .Date | time.Format "2006" }}">{{ .LinkTitle }}</a></li>
+    {{ end }}
+    {{ if $includeCollapsedYearItem -}}
+      <li class="tag__value__list-item"><a href="#older">{{ i18n "olderPagesSectionTitle" }}</a></li>
+    {{ end }}
+  </ul>
+</nav>