Avoid anchor name conflict with introduction page

_includes/sidebar.html

@@ -12,7 +12,7 @@
   <nav class="sidebar__nav">
     <div class="sidebar__nav-interior">
       {%- for section in sections -%}
-        <h3 class="section__header" id="{{ section }}">{{ section | capitalize }}</h3>
+        <h3 class="section__header" id="{{ section }}-section">{{ section | capitalize }}</h3>
 
         <ul class="section__links">
         {%- for item in site[section] -%}
@@ -30,4 +30,4 @@
     </script>
     {%- endif -%}
   </nav>
-</div>
+</div>