Moved css, js files from includes to assets.

assets/css/dark.css

@@ -0,0 +1,49 @@
+/* Dark mode */
+@media (prefers-color-scheme:dark) {
+  body {
+    background-color: #2d383e;
+  }
+
+  h1, h2, h3 {
+    color: white;
+  }
+
+  header {
+    background-color: #182329;
+  }
+
+  main {
+    color: white;
+  }
+
+  .menu {
+    color: white;
+  }
+
+  a {
+    color: #CC99FF;
+  }
+
+  a:hover {
+    color: white;
+    text-decoration: underline;
+  }
+
+  .content {
+    background-color: #182329;
+  }
+
+  main p {
+    color: #C8C8C8;
+  }
+
+  section {
+    background-color: #182329;
+  }
+
+  footer {
+    background-color: #182329;
+    color: #C8C8C8;
+  }
+
+}