title: Kotlin @Serializable annotation not working in IntelliJ
body: <p>I'm trying to use the <code>@Serializable</code> annotation in Kotlin. I can build the project with Gradle, but it's showing up red in IntelliJ and when I hover on the <code>@Serializable</code> annotation, there's a message saying:</p>
  
  <pre><code> kotlinx.serializable compiler plugin is not applied to the module, so this
   annotation would not be processed. Make sure you've setup your buildscript
   correctly and re-import project.
  </code></pre>
  
  <p>My <code>build.gradle.kts</code> file looks like this:</p>
  
  <pre><code>plugins {
      id("org.jetbrains.kotlin.jvm").version("1.3.50")
      id("org.jetbrains.kotlin.plugin.serialization") version "1.3.50"
      idea
  }
  
  repositories {
      jcenter()
  }
  
  dependencies {
      implementation("org.jetbrains.kotlin:kotlin-stdlib-jdk8")
      implementation(group = "com.charleskorn.kaml", name = "kaml", version = "0.12.0")
  
      testImplementation("org.jetbrains.kotlin:kotlin-test")
      testImplementation("org.jetbrains.kotlin:kotlin-test-junit")
  }
  </code></pre>
  
  <p>I have the most recent version of the Kotlin plugin (1.3.50) installed.</p>