I write some extension functon for JsonObject to r...

# serialization

[Luoqiaoyou]

I write some extension functon for JsonObject to reduce the effort of migration. if a Java JSONObject change to MPP JsonObject, i only need to change the create logic. The extension like this in Kotlin 1.3.72:

fun JsonObject.put(key: String, value: Long) {
    (content as MutableMap).put(key, JsonPrimitive(value))
}

but in Kotlin 1.4.0, content is private