Update page templating to centralize header and metatada, add 404 page

templates/404.html

@@ -0,0 +1,11 @@
+{% extends "base.html" %}
+
+{% block content %}
+<main id="main-content">
+  <div id="welcome-message">
+    <h2 id="blog-page-title">|| 404 Not Found ||</h2>
+    <h6 class="blog-post-date">These are not the frogs you're looking for 👋 🐸</h6>
+  </div>
+  <div class="dotted-border"></div>
+</main>
+{% endblock content %}