Increase social link spacing further, add About-me divider

Sidebar gap 6rem -> 10rem (previous doubling still read as too small).
About-me page: add a subtle .social-links-divider <hr> between the bio
text and the icon row (8rem gap above it, 3rem below to the icons) -
11rem total separation from the text, up from 3rem, plus a visual
break as requested.

templates/page.html

@@ -20,6 +20,7 @@
     {{ page.content }}
 
     {% if page.slug == 'about-me' %}
+    <hr class="social-links-divider">
     {% set social_links_variant = 'large' %}
     {% include "includes/social_links.html" %}
     {% endif %}