Only linkify h1 and h2 headings

Signed-off-by: Harsh Shandilya <msfjarvis@gmail.com>

layouts/_default/single.html

@@ -7,7 +7,7 @@
   {{ end }}
   </p>
   {{- with .Content -}}
-    {{ . | replaceRE "(<h[1-9] id=\"([^\"]+)\".+)(</h[1-9]+>)" `${1}<a href="#${2}" class="hanchor" ariaLabel="Anchor"> 🔗&#xFE0E;</a> ${3}` | safeHTML }}
+    {{ . | replaceRE "(<h[1-2] id=\"([^\"]+)\".+)(</h[1-9]+>)" `${1}<a href="#${2}" class="hanchor" ariaLabel="Anchor"> 🔗&#xFE0E;</a> ${3}` | safeHTML }}
   {{- end -}}
 </div>