fix: alt is not a valid attribute for 'a' tag

Author: ZakKemble

_includes/sidebar.html

@@ -5,7 +5,7 @@
 <div id="sidebar" class="d-flex flex-column align-items-end">
   <div class="profile-wrapper text-center">
     <div id="avatar">
-      <a href="{{ '/' | relative_url }}" alt="avatar" class="mx-auto">
+      <a href="{{ '/' | relative_url }}" class="mx-auto">
         {% if site.avatar != empty and site.avatar %}
           {% capture avatar_url %}
             {% if site.avatar contains '://' %}