Fixes the Quickstart With CMake guide to use webgpu_cpp_print.h

The example currently does not compile as it can't otherwise find the << operators for StringView.

R=cwallez@chromium.org

Change-Id: I135f6e51238209f3acce8db0433164c30f84ebd5
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/210795
Commit-Queue: Nicolas Chavez <nickchavez@google.com>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
diff --git a/docs/quickstart-cmake.md b/docs/quickstart-cmake.md
index 1cce6d8..00881b2 100644
--- a/docs/quickstart-cmake.md
+++ b/docs/quickstart-cmake.md
@@ -63,6 +63,7 @@
 
 ```cpp
 #include <webgpu/webgpu_cpp.h>
+#include <webgpu/webgpu_cpp_print.h>
 
 #include <cstdlib>
 #include <iostream>