Fix headings with an anchor in a summary (#2048)

* Fix headings with an anchor in a summary

* Create hip-readers-press.md

* Lint

Author: simurai

.changeset/hip-readers-press.md

@@ -0,0 +1,5 @@
+---
+"@primer/css": patch
+---
+
+Fix headings with an anchor in a summary

src/markdown/headings.scss

@@ -80,6 +80,11 @@
     h5,
     h6 {
       display: inline-block;
+
+      .anchor {
+        // stylelint-disable-next-line primer/spacing
+        margin-left: -40px;
+      }
     }
 
     h1,