feat(add): add kotlinx-io docs tree

Author: zoobestik

docs/kr.tree

@@ -311,6 +311,7 @@
 		<toc-element toc-title="Test library (kotlin.test)" href="https://kotlinlang.org/api/latest/kotlin.test/"/>
 		<toc-element toc-title="Coroutines (kotlinx.coroutines)" href="https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-core/"/>
 		<toc-element toc-title="Serialization (kotlinx.serialization)" href="https://kotlinlang.org/api/kotlinx.serialization/kotlinx-serialization-core/"/>
+		<toc-element toc-title="Kotlin I/O library (kotlinx-io)" href="https://kotlinlang.org/api/kotlinx-io/"/>
 		<toc-element toc-title="Date and time (kotlinx-datetime)" href="https://kotlinlang.org/api/kotlinx-datetime/"/>
 		<toc-element toc-title="JVM Metadata (kotlinx-metadata-jvm)" href="https://kotlinlang.org/api/kotlinx-metadata-jvm/"/>
 		<toc-element toc-title="Ktor" href="https://api.ktor.io/"/>