Styleguide: update heading styles

styleguide/assets/style/styleguide.scss

@@ -1,5 +1,30 @@
 @import "main";
 
+
+* {
+  box-sizing: border-box;
+}
+
+body {
+  margin: 0;
+  min-height: 100vh;
+  min-width: 100vw;
+}
+
+header {
+  padding: 1rem;
+}
+
+main {
+  max-width: min(var(--container-4xl), 100vw);
+  padding: 1rem;
+  overflow: hidden;
+
+  @media (min-width: $breakpoint-sm) {
+    padding-left: 2rem;
+  }
+}
+
 a {
   &.a-regular {
     color: var(--color-accent-1);
@@ -14,6 +39,11 @@ a {
   }
 }
 
+code, .code {
+  max-width: 100%;
+  overflow-x: auto;
+}
+
 .layout-column {
   display: flex;