add brew package to readme.md

closes #21

Author: crclark96

readme.md

@@ -124,6 +124,7 @@ $ cargo install choose
 ```
 
 Arch Linux:
+
 ```
 $ yay -S choose-rust-git
 ```
@@ -135,6 +136,12 @@ $ dnf copr enable atim/choose
 $ dnf install choose
 ```
 
+Homebrew:
+
+```
+$ brew install choose-rust
+```
+
 ### Benchmarking
 
 Benchmarking is performed using the [`bench` utility](https://github.com/Gabriel439/bench).