Update docs

Author: jvalkeal

spring-shell-docs/modules/ROOT/nav.adoc

@@ -65,12 +65,12 @@
 *** xref:tui/events/eventloop.adoc[]
 *** xref:tui/events/key.adoc[]
 *** xref:tui/events/mouse.adoc[]
-* xref:using-shell-customization.adoc[]
-** xref:using-shell-customization-styling.adoc[]
-** xref:using-shell-customization-logging.adoc[]
-** xref:using-shell-customization-commandnotfound.adoc[]
-** xref:using-shell-customization-singlecommand.adoc[]
-** xref:using-shell-customization-contextclose.adoc[]
+* xref:customization/index.adoc[]
+** xref:customization/styling.adoc[]
+** xref:customization/logging.adoc[]
+** xref:customization/commandnotfound.adoc[]
+** xref:customization/singlecommand.adoc[]
+** xref:customization/contextclose.adoc[]
 * xref:using-shell-execution.adoc[]
 * xref:using-shell-testing.adoc[]
 ** xref:using-shell-testing-basics.adoc[]

spring-shell-docs/modules/ROOT/pages/using-shell-customization-commandnotfound.adoc renamed to spring-shell-docs/modules/ROOT/pages/customization/commandnotfound.adoc

@@ -87,7 +87,7 @@ Or in non-interactive mode:
 include::example$getting-started-run-noninteractive.out[]
 ----
 
-TIP: Check out xref:using-shell-customization-logging.adoc[Logging] making logging to work
+TIP: Check out xref:/customization/logging.adoc[Logging] making logging to work
 better with shell apps.
 
 [[using-spring-shell-your-first-command]]