Update about.md

- Use jekyll linkedin_username variable (temporary)

_pages/about.md

@@ -24,4 +24,4 @@ With me, learning is a lifelong journey, more knowledge, more experience, more f
 
 I'm also interested in practical research, which can help me to learn and apply new technologies to solve real-world problems. I'm always looking for new opportunities to work on interesting projects, collaborate with other people, and learn new things.
 
-Connect with me on [LinkedIn](https://www.linkedin.com/in/dinhphu28) or [GitHub](https://github.com/dinhphu28)
+Connect with me on [LinkedIn](https://www.linkedin.com/in/{{site.linkedin_username}}) or [GitHub](https://github.com/dinhphu28)