Document logging of startup info

Closes gh-19026

Author: mbhave

spring-boot-project/spring-boot-docs/src/main/asciidoc/spring-boot-features.adoc

@@ -42,7 +42,11 @@ When your application starts, you should see something similar to the following
 
 By default, `INFO` logging messages are shown, including some relevant startup details, such as the user that launched the application.
 If you need a log level other than `INFO`, you can set it, as described in <<boot-features-custom-log-levels>>.
+The application version is determined using the implementation version from the main application class's package.
+Startup information logging can be turned off by setting `spring.main.log-startup-info` to `false`.
+This will also turn off logging of the application's active profiles.
 
+TIP: To add additional logging during startup, you can override `logStartupInfo(boolean)` in a subclass of `SpringApplication`.
 
 
 [[boot-features-startup-failure]]