Restore anchor for Supporters; #supporters URL links may be common

www/conservancy/templates/sponsors.html

@@ -57,6 +57,7 @@ any of its sponsors.</p>
   Sustainer program</a>.  Those who request public acknowledgment are listed
   here in order by the date when they first joined the Sustainer program:</p>
 
+<a id="supporters"/>
 <ul id="sustainers">
 <li>Anonymous ({{ anonymous_count }} people)</li>
 {% for ss in supporters %}