Updates docs

Signed-off-by: Timo Sand <timo.sand@f-secure.com>

Author: deiga

website/docs/r/repository_vulnerability_alerts.html.markdown

@@ -21,8 +21,8 @@ resource "github_repository" "example" {
 }
 
 resource "github_repository_vulnerability_alerts" "example" {
-  repository  = github_repository.example.name
-  enabled          = true
+  repository = github_repository.example.name
+  enabled    = true
 }
 ```
 
@@ -34,6 +34,12 @@ The following arguments are supported:
 
 - `enabled` - (Optional) Whether vulnerability alerts are enabled for the repository. Defaults to `true`.
 
+## Attribute Reference
+
+In addition to the above arguments, the following attributes are exported:
+
+- `repository_id` - The ID of the repository.
+
 ## Import
 
 Repository vulnerability alerts can be imported using the `repository_name`: