docs: make sidebar sticky

Author: keithamus

docs/_includes/reference_sidebar.html

@@ -1,5 +1,5 @@
 <aside class="col-lg-3 pl-4 pt-1 pb-1 bg-gray">
-  <nav>
+  <nav class="sticky top-100px">
     <ul class="f3-light ml-4">
       {% for item in sidebarItems %}
       <li class="py-1">

docs/_includes/sidebar.html

@@ -1,5 +1,5 @@
 <aside class="col-lg-3 pl-4 pt-1 pb-1 bg-gray">
-  <nav>
+  <nav class="sticky top-100px">
     <ol class="f3-light ml-4">
       {% for item in sidebarItems %}
       <li class="py-1">

docs/custom.css

@@ -4,6 +4,9 @@ code { font-size: 90% !important }
 h1, h2, h3, h4, h5 { margin: 1rem 0; width: 100%; }
 ul li { margin-left: 1rem }
 
+.sticky { position: sticky }
+.top-100px { top: 100px }
+
 /* No preference or prefers light */
 :root:not([data-prefers-color-scheme=dark]),
 html[data-prefers-color-scheme=light] {