Add reference to kotlin stdlib package list (#4093)

Author: daymxn

buildSrc/src/main/java/com/google/firebase/gradle/plugins/DackkaGenerationTask.kt

@@ -127,7 +127,8 @@ abstract class GenerateDocumentationTask @Inject constructor(
             "android" to "https://developer.android.com/reference/kotlin/",
             "google" to "https://developers.google.com/android/reference/",
             "firebase" to "https://firebase.google.com/docs/reference/kotlin/",
-            "coroutines" to "https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-core/"
+            "coroutines" to "https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-core/",
+            "kotlin" to "https://kotlinlang.org/api/latest/jvm/stdlib/"
         )
 
         return packageLists.get().map {