Add real-life example for turn_off script on wake-on-lan (#1535)

* Update switch.wake_on_lan.markdown

* Update switch.wake_on_lan.markdown

Suggested recipe for using turn_off to suspend a linux computer.

source/_components/switch.wake_on_lan.markdown

@@ -16,6 +16,7 @@ The `wake_on_lan` (WOL) switch platform allows you to turn on a [WOL](https://en
 
 <p class='note warning'>
 The WOL switch can only turn on your computer and monitor the state. There is no universal way to turn off a computer remotely. The `turn_off` variable is there to help you call a script when you have figured out how to remotely turn off your computer.
+See below for suggestions on how to do this.
 </p>
 
 To enable this switch in your installation, add the following to your `configuration.yaml` file:
@@ -33,3 +34,31 @@ Configuration variables:
 - **name** (*Optional*): The name of the switch. Default is 'Wake on LAN'.
 - **host** (*Optional*): The IP address or hostname to check the state of the device (on/off).
 - **turn_off** (*Optional*): Defines an [action](/getting-started/automation/) to run when the switch is turned off.
+
+## {% linkable_title Examples %}
+
+Here are some real life examples of how to use the **turn_off** variable.
+
+### {% linkable_title Suspending linux %}
+Suggested recipe for letting the turn_off script suspend a Linux computer (the **target**)
+from Home Assistant running on another Linux computer (the **server**).
+
+1. On the **server**, log in as the user account Home Assistant is running under. (I'm using `hass` in this example)
+2. On the **server**, create ssh keys by running `ssh-keygen`. Just press enter on all questions.
+3. On the **target**, create a new account that Home Assistant can ssh into: `sudo adduser hass`. Just press enter on all questions except password. I recommend using the same user name as on the server. If you do, you can leave out `hass@` in the ssh commands below.
+4. On the **server**, transfer your public ssh key by `ssh-copy-id hass@TARGET` where TARGET is your target machine's name or IP address. Enter the password you created in step 3.
+5. On the **server**, verify that you can reach your target machine without password by `ssh TARGET`.
+6. On the **target**, we need to let the hass user execute the program needed to suspend/shut down the target computer. I'm using `pm-suspend`, use `poweroff` to turn off the computer. First, get the full path: `which pm-suspend`. On my system, this is `/usr/sbin/pm-suspend`.
+7. On the **target**, using an account with sudo access (typically your main account), `sudo visudo`. Add this line last in the file: `hass ALL=NOPASSWD:/usr/sbin/pm-suspend`, where you replace `hass` with the name of your user on the target, if different, and `/usr/sbin/pm-suspend` with the command of your choice, if different.
+8. On the **server**, add the following to your configuration, replacing TARGET with the target's name:
+``` yaml
+switch:
+  - platform: wake_on_lan
+    name: "TARGET"
+    ...
+    turn_off:
+      service: shell_command.turn_off_TARGET
+
+shell_command:
+  turn_off_TARGET: 'ssh hass@TARGET sudo pm-suspend'
+```