Update doc appearance and link doc formats

Updated the ToC, banner, highlighting, and CSS styles to the last Spring standard.
Linked the HTML output to the PDF output and vice-versa.

spring-shell-docs/src/assembly/docs-zip.xml

@@ -8,15 +8,16 @@
     <includeBaseDirectory>false</includeBaseDirectory>
     <fileSets>
         <fileSet>
-            <directory>${project.build.directory}/generated-docs</directory>
-            <outputDirectory>reference/htmlsingle</outputDirectory>
+            <directory>${project.build.directory}/site/reference/html</directory>
+            <outputDirectory>site/reference/htmlsingle</outputDirectory>
             <includes>
                 <include>index.html</include>
+                <include>**/*</include>
             </includes>
         </fileSet>
         <fileSet>
-            <directory>${project.build.directory}/generated-docs</directory>
-            <outputDirectory>reference/pdf</outputDirectory>
+            <directory>${project.build.directory}/site/reference/pdf</directory>
+            <outputDirectory>site/reference/pdf</outputDirectory>
             <includes>
                 <include>index.pdf</include>
             </includes>
@@ -26,4 +27,4 @@
             <outputDirectory>api</outputDirectory>
         </fileSet>
     </fileSets>
-</assembly>
+</assembly>

spring-shell-docs/src/main/asciidoc/index.adoc

@@ -5,7 +5,15 @@ Eric Bottard;
 :icons: font
 :experimental: // For kbd: macro
 
-Version {project-version}
+ifdef::backend-html5[]
+*{projectVersion}*
+
+NOTE: This documentation is also available as https://docs.spring.io/spring-shell/docs/{projectVersion}/reference/pdf/index.pdf[PDF].
+endif::[]
+
+ifdef::backend-pdf[]
+NOTE: This documentation is also available as https://docs.spring.io/spring-shell/docs/{projectVersion}/reference/htmlsingle/index.html[HTML].
+endif::[]
 
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