Redesign docs layout

- New navbar, no more subnav. Migrated search and version picker into the main navbar and refreshed the design of it all, including the responsive toggles.
- New sidebar navigation is always expanded, and now features Bootstrap Icons alongside section headings
- Sidebar navigation autoscrolls to active link for better usability
- Subnav and navbar padding issues ironed out
- Enhanced the version picker in anticipation of v5.2: we can now link right to the same page in the previous version.
- Redesign callouts to add more color to our pages
- Collapse table of contents on mobile
- Cleanup and redesign button styles with CSS variables
- Update design for subnav version dropdown
- Update highlight and example to be full-width until md
- Improve the Added In badges
- Turn the ToC into a well on mobile

site/data/sidebar.yml

@@ -2,6 +2,8 @@
 # The logic for the sidebar generation is in "site/layouts/partials/docs-sidebar.html".
 
 - title: Getting started
+  icon: book-half
+  icon_color: indigo
   pages:
     - title: Introduction
     - title: Download
@@ -16,6 +18,8 @@
     - title: Contribute
 
 - title: Customize
+  icon: palette2
+  icon_color: pink
   pages:
     - title: Overview
     - title: Sass
@@ -26,6 +30,8 @@
     - title: Optimize
 
 - title: Layout
+  icon: grid-fill
+  icon_color: teal
   pages:
     - title: Breakpoints
     - title: Containers
@@ -37,6 +43,8 @@
     - title: CSS Grid
 
 - title: Content
+  icon: file-earmark-richtext
+  icon_color: gray
   pages:
     - title: Reboot
     - title: Typography
@@ -45,6 +53,8 @@
     - title: Figures
 
 - title: Forms
+  icon: ui-radios
+  icon_color: blue
   pages:
     - title: Overview
     - title: Form control
@@ -57,6 +67,8 @@
     - title: Validation
 
 - title: Components
+  icon: menu-button-wide-fill
+  icon_color: cyan
   pages:
     - title: Accordion
     - title: Alerts
@@ -84,6 +96,8 @@
     - title: Tooltips
 
 - title: Helpers
+  icon: magic
+  icon_color: orange
   pages:
     - title: Clearfix
     - title: Colored links
@@ -96,6 +110,8 @@
     - title: Vertical rule
 
 - title: Utilities
+  icon: braces-asterisk
+  icon_color: red
   pages:
     - title: API
     - title: Background
@@ -116,11 +132,15 @@
     - title: Visibility
 
 - title: Extend
+  icon: tools
+  icon_color: blue
   pages:
     - title: Approach
     - title: Icons
 
 - title: About
+  icon: globe2
+  icon_color: indigo
   pages:
     - title: Overview
     - title: Team