perf: allow no social links to be configured (#1494)

_includes/footer.html

@@ -8,9 +8,15 @@
   "
 >
   <p>
-    {{ '©' }}
+    {{- '©' }}
     <time>{{ 'now' | date: '%Y' }}</time>
+
+    {% if site.social.links %}
       <a href="{{ site.social.links[0] }}">{{ site.social.name }}</a>.
+    {% else %}
+      <em class="fst-normal">{{ site.social.name }}</em>.
+    {% endif %}
+
     {% if site.data.locales[include.lang].copyright.brief %}
       <span
         data-bs-toggle="tooltip"

_sass/addon/commons.scss

@@ -144,6 +144,10 @@ footer {
     }
   }
 
+  em {
+    @extend %text-highlight;
+  }
+
   p {
     text-align: center;
     margin-bottom: 0;