Add cpp documentary poster

Author: dpiparo

assets/images/cpp_documentary_poster.png

@@ -9,3 +9,10 @@ In 1979, Bjarne Stroustrup arrived at Bell Labs. What started as a small persona
 Squeezing out performance from hardware, while providing flexibility and expressiveness, today C++ is one of the most prominent programming languages used in science.
 
 [Cult.repo](https://www.cultrepo.com) shot a documentary about C++, featuring its creator, several world-class C++ experts, CERN, and also ROOT. Check out [the trailer](https://www.youtube.com/watch?v=NXwTRzywDSk), waiting for the release of the full documentary on June 4th!
+
+<center>
+    <img
+    src="{{'/assets/images/cpp_documentary_poster.png' | relative_url}}"
+    alt="Poster of the documentary"
+    style="width: 60%"/>
+</center>