Bump @primer/gatsby-theme-doctocat from 3.1.1 to 4.0.0 in /docs (#2191)

* Bump @primer/gatsby-theme-doctocat from 3.1.1 to 4.0.0 in /docs

* Create spicy-numbers-invent.md

* Move section titles as new NavItems

* Update docs/src/@primer/gatsby-theme-doctocat/nav.yml

Co-authored-by: Cole Bemis <colebemis@github.com>

Co-authored-by: Cole Bemis <colebemis@github.com>

Author: Josep Martins

.changeset/spicy-numbers-invent.md

@@ -0,0 +1,5 @@
+---
+"@primer/css": patch
+---
+
+Bump @primer/gatsby-theme-doctocat from 3.1.1 to 4.0.0 in /docs

docs/package.json

@@ -12,7 +12,7 @@
     "@babel/preset-react": "^7.16.7",
     "@koddsson/postcss-sass": "5.0.1",
     "@primer/components": "32.1.0",
-    "@primer/gatsby-theme-doctocat": "3.1.1",
+    "@primer/gatsby-theme-doctocat": "4.0.0",
     "@primer/octicons": "17.0.0",
     "@primer/octicons-react": "17.0.0",
     "@primer/primitives": "7.8.3",

docs/src/@primer/gatsby-theme-doctocat/nav.yml

@@ -1,11 +1,14 @@
-- title: Getting started
-  url: /getting-started
+- title: Introduction
   children:
+    - title: Getting started
+      url: /getting-started
     - title: Contributing
       url: /getting-started/contributing
 - title: Support
   url: /support
   children:
+    - title: Introduction
+      url: /support
     - title: Breakpoints
       url: /support/breakpoints
     - title: Spacing
@@ -19,6 +22,8 @@
 - title: Utilities
   url: /utilities
   children:
+    - title: Introduction
+      url: /utilities
     - title: Animations
       url: /utilities/animations
     - title: Borders
@@ -44,6 +49,8 @@
 - title: Components
   url: /components
   children:
+    - title: Introduction
+      url: /components
     - title: Alerts
       url: /components/alerts
     - title: Avatars
@@ -99,6 +106,8 @@
 - title: Marketing
   url: /marketing
   children:
+    - title: Introduction
+      url: /marketing
     - title: Buttons
       url: /components/marketing-buttons
     - title: Filters
@@ -112,6 +121,8 @@
 - title: Tools
   url: /tools
   children:
+    - title: Introduction
+      url: /tools
     - title: Deprecation data
       url: /tools/deprecations
     - title: Linting
@@ -123,6 +134,8 @@
 - title: Principles
   url: /principles
   children:
+    - title: Introduction
+      url: /principles
     - title: Accessibility
       url: /principles/accessibility
     - title: HTML