add crude encoding of PSN chunks

internal/encoders/chunk.go

@@ -0,0 +1,25 @@
+package encoders
+
+import "encoding/binary"
+
+func EncodeChunk(id uint16, chunkData []byte, hasSubchunks bool) []byte {
+
+	header := []byte{}
+
+	header = binary.LittleEndian.AppendUint16(header, id)
+
+	hasSubchunksBit := 0
+
+	if hasSubchunks {
+		hasSubchunksBit = 1
+	}
+
+	hasSubchunksBit = hasSubchunksBit << 15
+
+	header = binary.LittleEndian.AppendUint16(header, uint16(len(chunkData)+hasSubchunksBit))
+
+	bytes := header
+	bytes = append(bytes, chunkData...)
+
+	return bytes
+}