[Ai] Add support for serialization links (#7297)

Dackka can generate links to code in other packages/sites, but has to be
configured to do so. This change adds the necessary configuration so
links to `kotlinx.serialization` code are correctly generated when
processing refdocs.

Internal b/440622537

---------

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

Author: rlazo

kotlindoc/package-lists/serialization/package-list

@@ -0,0 +1,25 @@
+$dokka.format:html-v1
+$dokka.linkExtension:html
+
+module:kotlinx-serialization-cbor
+kotlinx.serialization.cbor
+module:kotlinx-serialization-core
+kotlinx.serialization
+kotlinx.serialization.builtins
+kotlinx.serialization.descriptors
+kotlinx.serialization.encoding
+kotlinx.serialization.modules
+module:kotlinx-serialization-hocon
+kotlinx.serialization.hocon
+kotlinx.serialization.hocon.serializers
+module:kotlinx-serialization-json
+kotlinx.serialization.json
+module:kotlinx-serialization-json-io
+kotlinx.serialization.json.io
+module:kotlinx-serialization-json-okio
+kotlinx.serialization.json.okio
+module:kotlinx-serialization-properties
+kotlinx.serialization.properties
+module:kotlinx-serialization-protobuf
+kotlinx.serialization.protobuf
+kotlinx.serialization.protobuf.schema

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

@@ -179,9 +179,10 @@ constructor(private val workerExecutor: WorkerExecutor) : GenerateDocumentationT
         "android" to "https://developer.android.com/reference/kotlin/",
         "androidx" 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/",
+        "firebase" to "https://firebase.google.com/docs/reference/kotlin/",
         "kotlin" to "https://kotlinlang.org/api/latest/jvm/stdlib/",
+        "serialization" to "https://kotlinlang.org/api/kotlinx.serialization/",
       )
 
     return packageLists