refactor: migrate tags and sitemap to /blog subdirectory

src/_components/tagslist.njk

@@ -1,7 +1,7 @@
 <div class="title">Catégories</div>
 <ul class="tags">
   {% for tag in collections.all | getAllTags | filterTagList %}
-    {% set tagUrl %}/tags/{{ tag | slugify }}/{% endset %}
+    {% set tagUrl %}/blog/tags/{{ tag | slugify }}/{% endset %}
     <li><a href="{{ tagUrl }}" class="post-tag">#{{ tag }}</a></li>
   {% endfor %}
 </ul>