added cactus theme files

hugo-content/themes/cactus/layouts/partials/header.html

@@ -0,0 +1,25 @@
+<header id="header">
+  <a href="{{ .Site.BaseURL }}">
+  {{ if (isset .Site.Params "gravatar") }}
+    <div id="logo" style="background-image: url(https://www.gravatar.com/avatar/{{ md5 .Site.Params.gravatar }}?s=100&d=identicon)"></div>
+  {{ else if (isset .Site.Params "logo") }}
+    <div id="logo" style="background-image: url({{ .Site.Params.logo | absURL }})"></div>
+  {{ else }}
+    <div id="logo" style="background-image: url({{ "images/logo.png" | absURL }})"></div>
+  {{ end}}
+  <div id="title">
+    <h1>{{ .Site.Title }}</h1>
+  </div>
+  </a>
+  <div id="nav">
+    <ul>
+      <li class="icon">
+        <a href="#" aria-label="Menu"><i class="fas fa-bars fa-2x" aria-hidden="true"></i></a>
+      </li>
+      {{ range .Site.Menus.main }}
+        <li><a href="{{ .URL }}">{{ .Name }}</a></li>
+      {{ end }}
+    </ul>
+  </div>
+</header>
+