feat: update stability css

Author: avivkeller

src/generators/legacy-html/assets/style.css

@@ -318,6 +318,10 @@ hr.line {
   margin: 0 0 1rem;
   padding: 1rem;
   line-height: 1.5;
+
+  position: sticky;
+  top: 3rem;
+  z-index: 1;
 }
 
 .api_stability p:first-of-type {
@@ -869,6 +873,10 @@ kbd {
     position: relative;
     top: 0;
   }
+
+  .api_stability {
+    top: 0;
+  }
 }
 
 @media not screen, (height <= 1000px) {