[doc] Include the output image in the README

README.md

@@ -2,7 +2,11 @@
 
 > This project is part of [Project Lemonade](https://rangho.dev/project-lemonade).
 
-Simple path tracer written in PowerShell, based on [Raytracing in One Weekend][1] online book.
+Simple path tracer written in PowerShell, based on [Raytracing in One Weekend][1]
+online book.
+Currently, the output image looks like this:
+
+<div align="center"><img src="output.png" /></div>
 
 ## Why PowerShell of all things
 
@@ -30,9 +34,12 @@ Provide `-ImageWidth` and -`ImageHeight` to set the output image's width and hei
 Invoke-Raytracing -ImageWidth 160 -ImageHeight 90
 ```
 
-Since all vector arithmetic is implemented in PowerShell, the rendering process is extremely slow.
-Currently there is no plan to accelerate individual calculations via .NET Numerics library.
-Speed is not part of the goal of this project, but it may be implemented in the future, after the base implementation is complete.
+Since all vector arithmetic is implemented in PowerShell, the rendering process is
+extremely slow.
+Currently there is no plan to accelerate individual calculations via .NET Numerics
+library.
+Speed is not part of the goal of this project, but it may be implemented in the future,
+after the base implementation is complete.
 
 [1]: https://raytracing.github.io/books/RayTracingInOneWeekend.html
 [2]: https://rangho.dev/project-lemonade/#okay-but-why-these-languages