Make version selector sticky

Author: Simran-B

site/themes/arangodb-docs-theme/layouts/_default/home.navigation.html

@@ -8,12 +8,12 @@
     {{- if $page.Pages }}
       {{- /* section (with child pages) */}}
       <li class="nav-section">
-        <div class="nav-section-header">
+        {{- $isVersioned := eq $page.RelPermalink "/arangodb/" }}
+        <div class="nav-section-header{{ if $isVersioned }} nav-section-header-versioned{{ end }}">
           <a class="link-nav" href="{{ .RelPermalink }}">{{ .Params.menuTitle | markdownify }}</a>
           <label class="expand-nav"><input type="checkbox"></label>
         </div>
-        {{- $isVersioned := eq $page.RelPermalink "/arangodb/" }}
-        {{ if $isVersioned }}
+        {{- if $isVersioned }}
           {{- partial "version-selector.html" . }}
           {{- range $versionSection := $page.Pages }}
             <ol class="nav-ol" data-version="{{ index (split $versionSection.Path "/") 2 }}">

site/themes/arangodb-docs-theme/static/css/theme.css

@@ -1973,6 +1973,12 @@ nav.pagination .next {
     display: flex;
 }
 
+.nav-section-header-versioned {
+    position: sticky;
+    top: -0.5rem;
+    background-color: var(--gray-950);
+}
+
 .nav-section > .nav-ol,
 .nav-section > .version-selector {
     display: none;
@@ -2059,4 +2065,6 @@ nav.pagination .next {
     border: none;
     width: calc(100% - 2rem);
     margin-left: 1rem;
+    position: sticky;
+    top: 2rem;
 }