update: add the overview section for GSoC with Kotlin (#4671)

* feat: add GSoC overview

* update: update wording

docs/kr.tree

@@ -423,8 +423,9 @@
 			<toc-element toc-title="Kotlin Foundation FAQ" href="https://kotlinfoundation.org/faq/"/>
 		</toc-element>
 		<toc-element toc-title="Google Summer of Code">
-			<toc-element topic="gsoc-2024.md"/>
-			<toc-element topic="gsoc-2023.md"/>
+			<toc-element toc-title="Overview" topic="gsoc-overview.md"/>
+			<toc-element toc-title="GSoC 2024" topic="gsoc-2024.md"/>
+			<toc-element toc-title="GSoC 2023" topic="gsoc-2023.md"/>
 		</toc-element>
 		<toc-element topic="security.md"/>
 		<toc-element topic="kotlin-pdf.md"/>

docs/topics/gsoc-overview.md

@@ -0,0 +1,13 @@
+[//]: # (title: Google Summer of Code with Kotlin)
+
+The Kotlin Foundation provides mentorship for Google Summer of Code (GSoC), 
+a global online program that introduces new contributors to open-source development.
+
+Learn more about GSoC on the [official Google Summer of Code website](https://summerofcode.withgoogle.com/).
+
+## Past GSoC projects with Kotlin
+
+You can explore past Google Summer of Code projects and ideas with Kotlin:
+
+* [](gsoc-2024.md)
+* [](gsoc-2023.md)