Introduce appendix section with version properties

With the introduction of Gradle we lost the list of version properties
that were previously in the spring-boot-dependencies POM and were also
linked inside the documentation. This commit introduces an appendix
section in the docs and links the appropriate places to the new section
to restore discoverability.

See gh-19898

spring-boot-project/spring-boot-docs/src/docs/asciidoc/appendix-dependency-versions.adoc

@@ -12,3 +12,11 @@ The following table provides details of all of the dependency versions that are
 When you declare a dependency on one of these artifacts without declaring a version, the version listed in the table is used.
 
 include::dependency-versions.adoc[]
+
+[[version-properties]]
+== Version Properties
+
+The following table provides all version properties that can be used to override the versions managed by Spring-Boot.
+Browse the {spring-boot-code}/spring-boot-project/spring-boot-dependencies/build.gradle[`spring-boot-dependencies` build.gradle] for a complete list of dependencies.
+
+include::version-properties.adoc[]

spring-boot-project/spring-boot-docs/src/docs/asciidoc/howto.adoc

@@ -2421,7 +2421,7 @@ Using this format lets the time be parsed into a `Date` and its format, when ser
 [[howto-customize-dependency-versions]]
 === Customize Dependency Versions
 If you use a Maven build that inherits directly or indirectly from `spring-boot-dependencies` (for instance, `spring-boot-starter-parent`) but you want to override a specific third-party dependency, you can add appropriate `<properties>` elements.
-Browse the {spring-boot-code}/spring-boot-project/spring-boot-dependencies/pom.xml[`spring-boot-dependencies`] POM for a complete list of properties.
+Browse the <<appendix-dependency-versions.adoc#version-properties, `Version properties`>> for a complete list of version properties.
 For example, to pick a different `slf4j` version, you would add the following property:
 
 [source,xml,indent=0,subs="verbatim,quotes,attributes"]

spring-boot-project/spring-boot-docs/src/docs/asciidoc/using-spring-boot.adoc

@@ -81,7 +81,7 @@ For instance, to upgrade to another Spring Data release train, you would add the
 	</properties>
 ----
 
-TIP: Check the {spring-boot-code}/spring-boot-project/spring-boot-dependencies/pom.xml[`spring-boot-dependencies` pom] for a list of supported properties.
+TIP: Check out the <<howto.adoc#howto-customize-dependency-versions, Customize Dependency Versions "`How-to`">> for more information.