Updates the README file to link to the newly created unit-4

Author: dbtreasure

README.md

@@ -23,7 +23,7 @@ Register via the **[signup form](https://huggingface.us17.list-manage.com/subscr
 | November 28, 2022  | [An Introduction to Diffusion Models](https://github.com/huggingface/diffusion-models-class/tree/main/unit1)| Introduction to Diffusers and Diffusion Models From Scratch |
 | December 12, 2022  | [Fine-Tuning and Guidance](https://github.com/huggingface/diffusion-models-class/tree/main/unit2) | Fine-Tuning a Diffusion Model on New Data and Adding Guidance |
 | December 21, 2022  | [Stable Diffusion](https://github.com/huggingface/diffusion-models-class/tree/main/unit3) | Exploring a Powerful Text-Conditioned Latent Diffusion Model |
-| January 2023 (TBC)  | Doing More with Diffusion | Advanced Techniques to Take Diffusion Further |
+| January 2023 (TBC)  | [Doing More with Diffusion] (https://github.com/huggingface/diffusion-models-class/tree/main/unit4) | Advanced Techniques to Take Diffusion Further |
 
 More information coming soon!