Add brew install deno to manual (#2407)

website/manual.md

@@ -106,10 +106,16 @@ iwr https://deno.land/x/install/install.ps1 | iex
 
 Using [Scoop](https://scoop.sh/) (windows):
 
-```
+```shellsession
 scoop install deno
 ```
 
+Using [Homebrew](https://brew.sh/) (mac):
+
+```shellsession
+brew install deno
+```
+
 Deno can also be installed manually, by downloading a tarball or zip file at
 [github.com/denoland/deno/releases](https://github.com/denoland/deno/releases).
 These packages contain just a single executable file. You will have to set the