refactor: migrate to /blog subdirectory

src/_pages/blog/index.njk

@@ -0,0 +1,18 @@
+---
+layout: home.njk
+eleventyNavigation:
+  key: Accueil
+  order: 1
+---
+<div class="main-content">
+  <h1 class="main-title">Blog numérique responsable</h1>
+  <p class="sub-title">par le collectif IT's on us</p>
+  <nav>
+    {% include "tagslist.njk" %}
+  </nav>
+  {% set articlesList = collections.articles | head(-5) %}
+  {% include "articlesList.njk" %}
+</div>
+<aside class="right-side">
+  {% include "other_links.njk" %}
+</aside>