Add documentation for chef-solo version pinning

website/source/docs/provisioners/chef-solo.html.md

@@ -110,6 +110,8 @@ configuration is actually required, but at least `run_list` is recommended.
     able to create directories and write into this folder. If the permissions
     are not correct, use a shell provisioner prior to this to configure it
     properly.
+- `version` (string) - The version of Chef to be installed. By default this is
+    empty which will install the latest version of Chef.
 
 ## Chef Configuration
 
@@ -177,7 +179,7 @@ install Chef in another way.
 
 ```text
 curl -L https://www.chef.io/chef/install.sh | \
-  {{if .Sudo}}sudo{{end}} bash
+  {{if .Sudo}}sudo{{end}} bash -s --{{if .Version}} -v {{.Version}}{{end}}
 ```
 
 When guest_os_type is set to "windows", Packer uses the following command to