fix: change some asset URLs

Make the URL relative to work also when the site is served from
a path

Author: gsanchietti

_includes/footer.html

@@ -19,7 +19,7 @@ <h2><strong>Contatti</strong></h2>
             </div>
             <div class="column is-3">
                 <a target="_blank" href="https://www.nethesis.it/">
-                    <img class="nethesis-logo-image" src="/assets/images/nethesis-logo-150.png">
+                    <img class="nethesis-logo-image" src="{{ site.baseurl }}/assets/images/nethesis-logo-150.png">
                 </a>
                 <p>
                     Da radici Open Source nascono nuove <br>

_includes/head.html

@@ -9,7 +9,7 @@
     <link rel="stylesheet" href="{{ site.baseurl }}/assets/css/bulma.min.css" />
     <link rel="stylesheet" href="{{ site.baseurl }}/assets/css/font-awesome/all.min.css" />
 
-    <link rel="shortcut icon" type="image/png" href="/assets/images/favicon-01.png"/>
+    <link rel="shortcut icon" type="image/png" href="{{ site.baseurl }}/assets/images/favicon-01.png"/>
 
     <meta name="google-site-verification" content="hR4RW8Fchx4T8o4dBtxRIyS1sexPxO_nAml4MBtpcsM" />
 </head>

assets/css/hero.css

@@ -144,7 +144,7 @@ footer li:before {
 
 .logos-images {
     background-color: #ffffff;
-    background-image: url("/assets/images/black-thread-light.png");
+    background-image: url("../images/black-thread-light.png");
     height: 140px;
 }