Add distributed training lab

src/SUMMARY.md

@@ -18,7 +18,7 @@
 
 - [2. The Transformer](lab2_transformer/lab2_transformer.md)
 
-- [Distributed Training]()
+- [3. Distributed Training](lab_training.md)
 
 ----
 - [Datacenter Networking]()

src/lab_training/lab3_training.md

+# 2. The Transformer
+
+Today's lab is about seeing distributed training in action, moving from the previous lab.
+We'll run it on a GPU and train a model to tell [tiny
+stories](https://arxiv.org/abs/2305.07759). Please follow the [jupyer lab](https://gitlab.cs.pub.ro/dcc1/dcc1.pages.upb.ro/-/blob/main/src/lab_training/Lab5-Distributed-training.ipynb)