Update README.md

Author: tommygonzaleza

exercises/00-Welcome/README.md

@@ -4,7 +4,7 @@ intro: "https://www.youtube.com/watch?v=BDKdUPDez-U"
 
 # Welcome to CSS Exercises!!
 
-My name is Alejandro Sanchez [@alesanchezr](twitter.com/alesanchezr). I'm really excited to have you here !! 🎉 😂
+My name is Alejandro Sanchez [@alesanchezr](https://twitter.com/alesanchezr). I'm really excited to have you here !! 🎉 😂
 Learning to code is hard, you will problably need coaching! DM me on twitter if you have any question.
 
 During this course you will be learning the following concepts: