Bump up Kotlin version to 1.8.21

Author: fzhinkin

README.md

@@ -3,7 +3,7 @@
 [![Kotlin Alpha](https://kotl.in/badges/alpha.svg)](https://kotlinlang.org/docs/components-stability.html)
 [![JetBrains incubator project](https://jb.gg/badges/incubator.svg)](https://confluence.jetbrains.com/display/ALL/JetBrains+on+GitHub)
 [![GitHub license](https://img.shields.io/badge/license-Apache%20License%202.0-blue.svg?style=flat)](http://www.apache.org/licenses/LICENSE-2.0)
-[![Kotlin](https://img.shields.io/badge/kotlin-1.7.20-blue.svg?logo=kotlin)](http://kotlinlang.org)
+[![Kotlin](https://img.shields.io/badge/kotlin-1.8.21-blue.svg?logo=kotlin)](http://kotlinlang.org)
 [![TeamCity build](https://img.shields.io/teamcity/build/s/KotlinTools_KotlinxIo_BuildAggregated.svg?server=http%3A%2F%2Fteamcity.jetbrains.com)](https://teamcity.jetbrains.com/viewType.html?buildTypeId=KotlinTools_KotlinxIo_BuildAggregated&guest=1)
 
 A multiplatform Kotlin library providing basic IO primitives. `kotlinx-io` is based on [Okio](https://github.com/square/okio) but does not preserve backward compatibility with it.

build.gradle.kts

@@ -13,7 +13,7 @@ plugins {
 
 buildscript {
     dependencies {
-        classpath("org.jetbrains.kotlin:kotlin-gradle-plugin:1.7.20")
+        classpath("org.jetbrains.kotlin:kotlin-gradle-plugin:1.8.21")
     }
 
     repositories {

buildSrc/build.gradle.kts

@@ -12,5 +12,5 @@ repositories {
 }
 
 dependencies {
-  implementation("org.jetbrains.kotlin:kotlin-gradle-plugin:1.7.20")
+  implementation("org.jetbrains.kotlin:kotlin-gradle-plugin:1.8.21")
 }

gradle.properties

@@ -5,5 +5,5 @@
 
 group=org.jetbrains.kotlinx
 version=0.2.0-alpha-dev1
-kotlin.version=1.7.20
+kotlin.version=1.8.21
 kotlin.code.style=official