add blog post link

This should help anyone who is new to conan and is trying to get this example working

Author: kxrur

examples/libraries/imgui/introduction/README.md

@@ -1,3 +1,6 @@
 # An introduction to the Dear ImGui library
 
 ![An introduction to the Dear ImGui library](assets/conan-imgui-widgets.gif)
+
+## Walkthough
+This example has a [blog post](https://blog.conan.io/2019/06/26/An-introduction-to-the-Dear-ImGui-library.html).