Add header

Signed-off-by: Nikolaos Karaolidis <nick@karaolidis.com>

layouts/partials/header.html

@@ -0,0 +1,14 @@
+<header class="header">
+  <div class="header-container">
+    <div class="site-title">
+      <a href="{{- "/" | relURL -}}">{{ .Site.Title }}</a>
+    </div>
+    <nav class="nav">
+      <ul>
+        {{ range .Site.Params.navigation }}
+          <li><a href="{{- .url -}}">{{ .name }}</a></li>
+        {{ end }}
+      </ul>
+    </nav>
+  </div>
+</header>