Add task to generate Kotlinlang reference

Based on the template from
https://github.com/JetBrains/kotlin-web-site/tree/master/dokka-templates.
Template itself is updated frequently and should be added by CI
configuration.

Generated reference has versioning support. Older generated references
should put into:
<project_dir>/<build_dir>/dokka/kotlinlangDocumentationOld

^KT-55520 Fixed

libraries/tools/kotlin-gradle-plugin-api/build.gradle.kts

@@ -5,7 +5,8 @@ plugins {
 }
 
 configureDokkaPublication(
-    shouldLinkGradleApi = true
+    shouldLinkGradleApi = true,
+    configurePublishingToKotlinlang = true,
 )
 
 dependencies {

libraries/tools/kotlin-gradle-plugin-api/dokka-template/ReadMe.md

@@ -0,0 +1,13 @@
+# Dokka's template customization
+
+To provide unified navigation for all parts of [kotlinlang.org](https://kotlinlang.org/),
+the Kotlin Website Team uses this directory to place custom templates in this folder
+during the website build time on TeamCity.
+
+It is not practical to place these templates in the kotlinx-datetime repository because they change from time to time
+and aren't related to the plugin's release cycle.
+
+The folder is defined as a source for custom templates by the templatesDir property through Dokka's plugin configuration.
+
+[Here](https://kotlin.github.io/dokka/1.7.20/user_guide/output-formats/html/#custom-html-pages), you can
+find more about the customization of Dokka's HTML output.