examples/seq2seq supports translation (#5202)

examples/seq2seq/finetune.sh

@@ -0,0 +1,14 @@
+# Add parent directory to python path to access lightning_base.py
+export PYTHONPATH="../":"${PYTHONPATH}"
+
+# the proper usage is documented in the README, you need to specify data_dir, output_dir and model_name_or_path
+python finetune.py \
+    --learning_rate=3e-5 \
+    --fp16 \
+    --gpus 1 \
+    --do_train \
+    --do_predict \
+    --n_val 1000 \
+    --val_check_interval 0.1 \
+    --sortish_sampler \
+    $@