Fix logic to use url rather than title (title is not always unique)

_includes/post/prev-next.html

@@ -3,13 +3,15 @@
     {% for category in site.categories %}{% assign catg_name = category.first
     %}{% if catg_name == page.categories[0] %}{% assign catg_posts =
     category.last %}{% endif %}{% endfor %}{% for post in catg_posts %}{% if
-    post.title == page.title %}{% unless forloop.last %}{% assign prev =
+    post.url == page.url %}{% unless forloop.last %}{% assign prev =
     catg_posts[forloop.index] %}<a href="{{ prev.url }}" class="post-prev btn">
       {% include icons/chevron-left.svg %}
       <span class="post-prev-title">Older</span> </a
     >{% endunless %}{% endif %}{% assign next = post %}{% endfor %}{% for post
-    in catg_posts %}{% if post.title == page.title %}{% unless forloop.first
-    %}<a href="{{ next.url }}" class="post-next btn">
+    in catg_posts %}{% if post.url == page.url %}{% unless forloop.first %}<a
+      href="{{ next.url }}"
+      class="post-next btn"
+    >
       <span class="post-next-title">Newer</span> {% include
       icons/chevron-right.svg %}</a
     >{% endunless %}{% endif %}{% assign next = post %}{% endfor %}