feat: migrate prev/next pager to Hugo's cascade system

New cascade front matter param: .Params.pager

Close #2737
See #2395

starters/blog/config/_default/config.yaml

@@ -14,6 +14,7 @@ cascade:
   # Blog post options
   - _target:
       path: /post/**
+    pager: true
     editable: true
     reading_time: true
     commentable: true

wowchemy/layouts/partials/book_layout.html

@@ -83,9 +83,9 @@
           {{ partial "tags.html" . }}
 
           {{/* Show next/previous pages by default. */}}
-          {{ if ne site.Params.book_section_pager false }}
+          {{ if ne .Params.pager false }}
           <div class="article-widget">
-            {{ partial "section_pager" . }}
+            {{ partial "components/pager" . }}
           </div>
           {{ end }}
         </div>

wowchemy/layouts/partials/page_footer.html

@@ -4,9 +4,9 @@
 {{ partial "page_author" . }}
 {{ partial "comments" . }}
 
-{{ if site.Params.section_pager }}
+{{ if .Params.pager }}
 <div class="article-widget">
-  {{ partial "section_pager" . }}
+  {{ partial "components/pager" . }}
 </div>
 {{ end }}