fix: prevent the search bar from moving when focused (#2336)

Author: MrAnno

_includes/topbar.html

@@ -1,6 +1,6 @@
 <!-- The Top Bar -->
 
-<header id="topbar-wrapper" aria-label="Top Bar">
+<header id="topbar-wrapper" class="flex-shrink-0" aria-label="Top Bar">
   <div
     id="topbar"
     class="d-flex align-items-center justify-content-between px-lg-3 h-100"