Update README.md

Author: ryoppippi

README.md

@@ -20,13 +20,24 @@ zig build -Drelease-fast=true
 - OS: macOS 12.4（21F79）
 - Zig: 0.10.0-dev.3007+6ba2fb3db
 
+Before Multithreading [9305860](https://github.com/ryoppippi/Ray-Tracing-in-One-Weekend.zig/tree/week1.2)
+
 ```sh
 ________________________________________________________
 Executed in  879.32 secs    fish           external
    usr time  863.33 secs   35.00 micros  863.33 secs
    sys time   15.33 secs  550.00 micros   15.33 secs
 ```
 
+After Multithreading
+
+```sh
+________________________________________________________
+Executed in  190.77 secs    fish           external
+   usr time   22.87 mins   47.00 micros   22.87 mins
+   sys time    0.09 mins  825.00 micros    0.09 mins
+```
+
 ## License
 
 MIT