Add `MessageSource.time`

mirai-core-qqandroid/src/commonMain/kotlin/net/mamoe/mirai/qqandroid/message/MessageSourceFromMsg.kt

@@ -21,6 +21,7 @@ import net.mamoe.mirai.qqandroid.network.protocol.data.proto.SourceMsg
 internal inline class MessageSourceFromServer(
     val delegate: ImMsgBody.SourceMsg
 ) : MessageSource {
+    override val time: Long get() = delegate.time.toLong() and 0xFFFFFFFF
     override val messageUid: Long get() = delegate.pbReserve.loadAs(SourceMsg.ResvAttr.serializer()).origUids!!
     override val sourceMessage: MessageChain get() = delegate.toMessageChain()
     override val senderId: Long get() = delegate.senderUin
@@ -32,6 +33,7 @@ internal inline class MessageSourceFromServer(
 internal inline class MessageSourceFromMsg(
     val delegate: MsgComm.Msg
 ) : MessageSource {
+    override val time: Long get() = delegate.msgHead.msgTime.toLong() and 0xFFFFFFFF
     override val messageUid: Long get() = delegate.msgBody.richText.attr!!.random.toLong()
     override val sourceMessage: MessageChain get() = delegate.toMessageChain()
     override val senderId: Long get() = delegate.msgHead.fromUin

mirai-core/src/commonMain/kotlin/net.mamoe.mirai/message/data/MessageSource.kt

@@ -31,6 +31,11 @@ interface MessageSource : Message {
      */
     val messageUid: Long
 
+    /**
+     * 发送时间, 单位为秒
+     */
+    val time: Long
+
     /**
      * 发送人号码
      */