chore: change pkgdown site structure

.github/playbook_intro.md

@@ -1,6 +1,6 @@
-# Employee Experience Analysis Map
+# wpa R Playbook
 
-This page offers a 'map' for the Workplace Analytics analyst - a guide to what analyses or functions could be useful when exploring a particular area of Workplace Analytics. This map is divided into the following sections.
+This page offers a **playbook for the Workplace Analytics analyst**: a guide to what analyses or functions could be useful when exploring a particular area of Workplace Analytics. This map is divided into the following sections.
 
 - [Ways of Working](#ways-of-working)
 - [Employee Wellbeing](#employee-wellbeing)

_pkgdown.yml

@@ -43,6 +43,9 @@ navbar:
     reference:
       text: Reference
       href: reference/index.html
+    playbook:
+      text: Playbook
+      href: playbook_intro.html
     contributing:
       text: Contribute
       menu: