chore: add resource link to cpp >> introduction:what-is-cpp

src/data/roadmaps/cpp/content/100-introduction/100-what-is-cpp.md

@@ -42,4 +42,6 @@ int main() {
 }
 ```
 
-In the above program, we define a simple function `add` and a class `Calculator` with a member function `multiply`. The `main` function demonstrates how to use these to perform basic arithmetic.
+In the above program, we define a simple function `add` and a class `Calculator` with a member function `multiply`. The `main` function demonstrates how to use these to perform basic arithmetic.
+
+- [C++ Tutorial for Beginners - Full Course](https://youtu.be/vLnPwxZdW4Y)