Add camera settings for book 1 final scene

Resolves #344

Author: hollasch

books/RayTracingInOneWeekend.html

@@ -2671,6 +2671,14 @@
     int main() {
         ...
         auto world = random_scene();
+
+        vec3 lookfrom(13,2,3);
+        vec3 lookat(0,0,0);
+        vec3 vup(0,1,0);
+        auto dist_to_focus = 10.0;
+        auto aperture = 0.1;
+
+        camera cam(lookfrom, lookat, vup, 20, aspect_ratio, aperture, dist_to_focus);
         ...
     }
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