update powershell docs to include reference to the new winrmpassword template variable

website/source/docs/provisioners/powershell.html.md

@@ -72,7 +72,16 @@ Optional parameters:
 -   `environment_vars` (array of strings) - An array of key/value pairs to
     inject prior to the execute\_command. The format should be `key=value`.
     Packer injects some environmental variables by default into the
-    environment, as well, which are covered in the section below.
+    environment, as well, which are covered in the section below. If you are
+    using AWS and would like to use the randomly-generated unique
+    If you are running on AWS and would like to access the AWS-generated
+    Administrator password that Packer uses to connect to the instance via
+    WinRM, you can use the template variable `{{.WinRMPassword}}` to set this
+    as an environment variable. For example:
+
+    ```json
+    "environment_vars": "WINRMPASS={{.WinRMPassword}}",
+    ```
 
 -   `execute_command` (string) - The command to use to execute the script. By
     default this is as follows:
@@ -89,7 +98,15 @@ Optional parameters:
 
 -   `elevated_user` and `elevated_password` (string) - If specified, the
     PowerShell script will be run with elevated privileges using the given
-    Windows user.
+    Windows user. If you are running a build on AWS and would like to run using
+    the AWS-generated password that Packer uses to connect to the instance via,
+    WinRM, you may do so by using the template variable {{.WinRMPassword}}.
+    For example:
+
+    ``` json
+    "elevated_user": "Administrator",
+    "elevated_password": "{{.WinRMPassword}}",
+    ```
 
 -   `remote_path` (string) - The path where the script will be uploaded to in
     the machine. This defaults to "c:/Windows/Temp/script.ps1". This value must