doc: Fix anchor link dead zone

Author: adriansmares

doc/themes/the-things-stack/assets/css/common/global.scss

@@ -127,14 +127,8 @@ table.fixed td { overflow: auto; }
 
 // Fix for anchor link headbutting https://css-tricks.com/hash-tag-links-padding/
 .content {
-  h2::before, h3::before, h4::before {
-    display: block;
-    content: " ";
-    margin-top: -$navbar-height - 1rem;
-    height: $navbar-height + 1rem;
-    visibility: hidden;
-    pointer-events: none;
-    z-index: -1;
+  h2, h3, h4 {
+    scroll-margin-top: 0.25em;
   }
 }