Create marker for Gradle Plugin Portal for kotlinx-serialization compiler plugin

#KT-27612 fixed

libraries/tools/kotlin-serialization/build.gradle

@@ -35,3 +35,12 @@ artifacts {
 }
 
 javadocJar()
+
+pluginBundle {
+    plugins {
+        kotlinSerialization {
+            id = 'org.jetbrains.kotlin.plugin.serialization'
+            description = displayName = 'Kotlin compiler plugin for kotlinx.serialization library'
+        }
+    }
+}

libraries/tools/kotlin-serialization/plugin-marker/build.gradle

@@ -0,0 +1,3 @@
+apply from: "$rootDir/libraries/tools/gradle-tools/pluginMarkers.gradle"
+
+pluginMarkerProject('kotlin-serialization')