move types out of decoders package

internal/chunks/packet_header_chunk.go

@@ -0,0 +1,14 @@
+package chunks
+
+type PacketHeaderChunkData struct {
+	PacketTimestamp  uint64
+	VersionHigh      uint8
+	VersionLow       uint8
+	FrameId          uint8
+	FramePacketCount uint8
+}
+
+type PacketHeaderChunk struct {
+	Chunk Chunk
+	Data  PacketHeaderChunkData
+}