Feature Github Wiki more prominently

Issue: SPR-17469

src/docs/asciidoc/index.adoc

@@ -2,16 +2,15 @@
 :doc-root: https://docs.spring.io
 :api-spring-framework: {doc-root}/spring-framework/docs/{spring-version}/javadoc-api/org/springframework
 
-Welcome to the Spring Framework reference documentation!
-
-Please read the <<overview.adoc#overview,*Overview*>> for a quick introduction including brief history,
-design philosophy, where to ask questions, and tips to get started. For information on
-"What's New", or "Migrating from previous versions", check the
+****
+_What's New_, _Upgrade Notes_, _Supported Versions_, and other topics, independent of
+release cadence, are maintained externaly on the project's
 https://github.com/spring-projects/spring-framework/wiki[*Github Wiki*].
-
-The reference documentation is divided into several sections:
+****
 
 [horizontal]
+<<overview.adoc#overview,*Overview*>> :: history, design philosophy,feedback,
+getting started.
 <<core.adoc#spring-core,Core>> :: IoC container, Events, Resources, i18n, Validation,
 Data Binding, Type Conversion, SpEL, AOP.
 <<testing.adoc#testing,Testing>> :: Mock objects, TestContext framework,