examples/seq2seq supports translation (#5202)

examples/seq2seq/run_distiller.sh

@@ -0,0 +1,10 @@
+# Add parent directory to python path to access lightning_base.py
+export PYTHONPATH="../":"${PYTHONPATH}"
+
+python distillation.py \
+--learning_rate=3e-4 \
+--do_train \
+--do_predict \
+--fp16 \
+--val_check_interval 0.1 \
+$@