docgen: implement doc link resolution in current module (#18642)

config/nimdoc.cfg

@@ -56,6 +56,17 @@ $seeSrc
 </div>
 """
 
+# A wrapper of a few overloaded `doc.item`s with the same basic name
+# * $header_plain - see above
+# * $overloadGroupName - the anchor for this whole group
+# * $content - string containing `doc.item`s themselves
+doc.item2 = """
+
+<div id="$overloadGroupName">
+$content
+</div>
+"""
+
 # Chunk of HTML emitted for each entry in the HTML table of contents.
 # See doc.item for available substitution variables.