chore: add tldr about the latest Kotlin version (#4774)

* chore: add tldr about the latest Kotlin version

* chore: add a var for the latest What's new in Kotlin

Author: koshachy

docs/topics/releases.md

@@ -1,5 +1,10 @@
 [//]: # (title: Kotlin releases)
 
+<tldr>
+    <p>Latest Kotlin version: <strong>%kotlinVersion%</strong></p>
+    <p>See <a href="%kotlinLatestWhatsnew%">What's new in Kotlin %kotlinVersion%</a> for details</p>
+</tldr>
+
 Since Kotlin 2.0.0, we ship the following types of releases:
 
 * _Language releases_ (2._x_._0_) that bring major changes in the language and include tooling updates. Released once in 6 months.

docs/v.list

@@ -8,6 +8,7 @@
     <var name="kotlinVersion" value="2.1.20" type="string"/>
     <var name="kotlinReleaseDate" value="March 20, 2025" type="string"/>
     <var name="kotlinLatestUrl" value="https://github.com/JetBrains/kotlin/releases/tag/v2.1.20" type="string"/>
+    <var name="kotlinLatestWhatsnew" value="whatsnew2120.md" type="string"/>
 
     <var name="languageVersion" value="2.1" type="string"/>
     <var name="apiVersion" value="2.1" type="string"/>