Add header links to Ninjadev accounts

To make it easier to find our general presence on Github, Pouet,
YouTube, not just via our individual demos.

index.html

@@ -41,7 +41,7 @@
       background: #1d3459;
       position: relative;
       overflow: hidden;
-      margin-bottom: 40px;
+      margin-bottom: 20px;
       text-align: center;
       color: white;
     }
@@ -95,6 +95,13 @@
       transform: translate3d(0px, 0px, 2px);
     }
 
+    .external-links {
+      display: flex;
+      justify-content: center;
+      gap: 16px;
+      margin-bottom: 30px;
+    }
+
     .demo {
       max-width: 625px;
       margin: 15px auto 30px;
@@ -157,6 +164,33 @@
       </div>
     </div>
 
+    <div class="external-links">
+      <a href="https://github.com/ninjadev/">
+        <img
+          src="/assets/images/github.svg"
+          alt="GitHub"
+          width="20"
+          height="20"
+        />
+      </a>
+      <a href="https://www.pouet.net/groups.php?which=11702">
+        <img
+          src="/assets/images/pouet.svg"
+          alt="Pouet"
+          width="20"
+          height="20"
+        />
+      </a>
+      <a href="https://www.youtube.com/@ninjadev_demos">
+        <img
+          src="/assets/images/youtube.svg"
+          alt="Pouet"
+          width="20"
+          height="20"
+        />
+      </a>
+    </div>
+
     {% for post in site.posts %}
       <div class="demo">
         <div class="aspect-16-9">