Context close docs

- Relates spring-projects#863

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

@@ -62,6 +62,7 @@
 ** 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:using-shell-execution.adoc[]
 * xref:using-shell-testing.adoc[]
 ** xref:using-shell-testing-basics.adoc[]

spring-shell-docs/modules/ROOT/pages/using-shell-customization-contextclose.adoc

@@ -0,0 +1,25 @@
+[[using-shell-customization-contextclose]]
+= Context Close
+:page-section-summary-toc: 1
+
+ifndef::snippets[:snippets: ../../test/java/org/springframework/shell/docs]
+
+Command execution logic happens via Spring Boot's `ApplicationRunner` beans.
+Normally Spring `ApplicationContext` closes automatically after these runner
+beans has been processed unless there is something what keeps it alive like
+use of `@EnableScheduling` or generally speaking there are threads which
+don't die automatically.
+
+It is possible to add configuration property `spring.shell.context.close`
+which registers `ApplicationListener` for `ApplicationReadyEvent` and requests
+context close after shell has completed its execution logic.
+
+[source, yaml]
+----
+spring:
+  shell:
+    context:
+      close: true
+----
+
+NOTE: This setting is not enabled by default.