fix(css): add scroll-margin-top to headings for sticky header offset

src/styles/global.css

@@ -179,6 +179,7 @@ h1, h2, h3, h4 {
   line-height: 1.25;
   letter-spacing: -0.02em;
   font-weight: 700;
+  scroll-margin-top: 5rem;
 }
 h1 { font-size: 2rem; margin: 0 0 1rem; }
 h2 { font-size: 1.4rem; margin: 2.25rem 0 0.75rem; }