website: add heroku drain

cc/ @bmarini

website/source/docs/providers/heroku/r/drain.html.markdown

@@ -0,0 +1,34 @@
+---
+layout: "heroku"
+page_title: "Heroku: heroku_drain"
+sidebar_current: "docs-heroku-resource-drain"
+---
+
+# heroku\_drain
+
+Provides a Heroku Drain resource. This can be used to
+create and manage Log Drains on Heroku.
+
+## Example Usage
+
+```
+# Create a new heroku drain
+
+resource "heroku_drain" "default" {
+    app = "test-app"
+    url = "syslog://terraform.example.com:1234"
+}
+
+## Argument Reference
+
+The following arguments are supported:
+
+* `url` - (Required) The URL for Heroku to drain your logs to
+* `app` - (Required) The Heroku app to link to.
+
+## Attributes Reference
+
+The following attributes are exported:
+
+* `token` - The unique token for your created drain
+

website/source/layouts/heroku.erb

@@ -23,6 +23,10 @@
 
                     <li<%= sidebar_current("docs-heroku-resource-domain") %>>
 					<a href="/docs/providers/heroku/r/domain.html">heroku_domain</a>
+                    </li>
+
+                    <li<%= sidebar_current("docs-heroku-resource-drain") %>>
+                    <a href="/docs/providers/heroku/r/drain.html">heroku_drain</a>
                     </li>
 				</ul>
 				</li>