fix(style): introduce semiBoldWeight and various improvements to reduce CLS

quartz/styles/base.scss

@@ -54,7 +54,7 @@ ul,
 }
 
 a {
-  font-weight: $boldWeight;
+  font-weight: $semiBoldWeight;
   text-decoration: none;
   transition: color 0.2s ease;
   color: var(--secondary);

quartz/styles/callouts.scss

@@ -157,6 +157,6 @@
   }
 
   .callout-title-inner {
-    font-weight: $boldWeight;
+    font-weight: $semiBoldWeight;
   }
 }

quartz/styles/variables.scss

@@ -5,4 +5,5 @@ $sidePanelWidth: 380px;
 $topSpacing: 6rem;
 $fullPageWidth: $pageWidth + 2 * $sidePanelWidth;
 $boldWeight: 700;
+$semiBoldWeight: 600;
 $normalWeight: 400;