add model configuration

config.json

@@ -0,0 +1,13 @@
+{
+  "vocab_size": 17,
+  "pad_id": 14,
+  "bos_id": 13,
+  "eos_id": 15,
+  "max_seq_len": 128,
+  "d_model": 256,
+  "nhead": 4,
+  "num_encoder_layers": 2,
+  "num_decoder_layers": 2,
+  "dim_feedforward": 1024,
+  "dropout": 0.0
+}