Changelog: Markdeep's class=pixel fix

Author: hollasch

CHANGELOG.md

@@ -11,6 +11,7 @@ Change Log -- Ray Tracing in One Weekend
 - New: Add explanation for padding `aarect` in the zero dimension (#488)
 - Change: Minor change to use new `point3` and `color` type aliases for `vec3` (#422)
 - Change: Renamed `constant_texture` to `solid_color`, add RGB constructor (#452)
+- Change: Books use Markdeep's image class=pixel for rendered image fidelity (#498)
 
 ### _In One Weekend_
 - Fix: Update image and size for first PPM image