add missing links

Author: vivganes

units/en/unit0/introduction.mdx

@@ -104,9 +104,9 @@ Since there's a deadline, we provide you a recommended pace:
 
 To get the most out of the course, we have some advice:
 
-1. Join study groups in Discord: studying in groups is always easier. To do that, you need to join our discord server and verify your account.
-2. **Do the quizzes and assignments**: the best way to learn is through hands-on practice and self-assessment.
-3. **Define a schedule to stay in sync**: you can use our recommended pace schedule below or create yours.
+1. [Join study groups in Discord](https://discord.gg/UrrTSsSyjb): Studying in groups is always easier. To do that, you need to join our discord server and verify your account.
+2. **Do the quizzes and assignments**: The best way to learn is through hands-on practice and self-assessment.
+3. **Define a schedule to stay in sync**: You can use our recommended pace schedule below or create yours.
 
 ![Course advice](https://huggingface.co/datasets/mcp-course/images/resolve/main/unit0/3.png)
 
@@ -128,12 +128,12 @@ Ben is a Machine Learning Engineer at Hugging Face who focuses building LLM appl
 
 Contributions are **welcome** 🤗
 
-* If you _found a bug 🐛 in a notebook_, please open an issue and **describe the problem**.
-* If you _want to improve the course_, you can open a Pull Request.
-* If you _want to add a full section or a new unit_, the best is to open an issue and **describe what content you want to add before starting to write it so that we can guide you**.
+* If you _found a bug 🐛 in a notebook_, please [open an issue](https://github.com/huggingface/mcp-course/issues/new) and **describe the problem**.
+* If you _want to improve the course_, you can [open a Pull Request](https://github.com/huggingface/mcp-course/pulls).
+* If you _want to add a full section or a new unit_, the best is to [open an issue](https://github.com/huggingface/mcp-course/issues/new) and **describe what content you want to add before starting to write it so that we can guide you**.
 
 ## I still have questions
 
 Please ask your question in our discord server #mcp-course-questions.
 
-Now that you have all the information, let's get on board ⛵ 
+Now that you have all the information, let's get on board ⛵