Clarify random_double(min,max) implementation

Resolves #1681

Author: hollasch

CHANGELOG.md

@@ -5,6 +5,7 @@ Change Log / Ray Tracing in One Weekend
 
 ### Common
   - Fix    -- Fixed some dangling references to `random_in_unit_sphere()` (#1637)
+  - Fix    -- Clarify `uniform_real_distribution` usage for `random_double()` (#1680)
 
 ### In One Weekend
   - Fix    -- Fix equation for refracted rays of non-unit length (#1644)

books/RayTracingInOneWeekend.html

@@ -2044,6 +2044,13 @@
     }
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++
 
+    inline double random_double(double min, double max) {
+        // Returns a random real in [min,max).
+        return min + (max-min)*random_double();
+    }
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++
+
+
     ...
 
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~