Partial: Move changelog-date to theme from documentation

Author: lamATnginx

layouts/partials/changelog-date.html

@@ -0,0 +1,10 @@
+{{ $changelogContent := readFile "content/nginx-one/changelog.md" }}
+{{ $maxNumLogs := 3 }}
+{{ $headings := first $maxNumLogs (findRE `(?m)^##\s(.+)$` $changelogContent) }}
+<ul>
+  {{ range $headings }}
+  {{ $title := replaceRE "^##\\s" "" . }}
+  <li><a href="{{ absURL "nginx-one/changelog/" }}#{{urlize $title}}">{{ $title }}</a></li>
+  {{ end }}  
+  <li><a href="{{ absURL "nginx-one/changelog/" }}">Older...</a></li>
+</ul>