Document favicon support

Closes gh-7903

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

@@ -1686,7 +1686,7 @@ The auto-configuration adds the following features on top of Spring's defaults:
 * Support for `HttpMessageConverters` (see below).
 * Automatic registration of `MessageCodesResolver` (see below).
 * Static `index.html` support.
-* Custom `Favicon` support.
+* Custom `Favicon` support (see below).
 * Automatic use of a `ConfigurableWebBindingInitializer` bean (see below).
 
 If you want to keep Spring Boot MVC features, and
@@ -1886,6 +1886,14 @@ and in Spring Framework's {spring-reference}/#mvc-config-static-resources[refere
 
 
 
+[[boot-features-spring-mvc-favicon]]
+==== Custom Favicon
+Spring Boot looks for a `favicon.ico` in the configured static content locations and the
+root of the classpath (in that order). If such file is present, it is automatically used
+as the favicon of the application.
+
+
+
 [[boot-features-spring-mvc-web-binding-initializer]]
 ==== ConfigurableWebBindingInitializer
 Spring MVC uses a `WebBindingInitializer` to initialize a `WebDataBinder` for a particular