fix(group-mapping): Improve the documentation (#518)

* refactor on examples

Author: Shadow649

website/docs/r/group_mapping.md

@@ -14,6 +14,8 @@ Creates a group mapping in Sysdig.
 
 ## Example Usage
 
+### Regular users
+
 ```terraform
 resource "sysdig_group_mapping" "my_group" {
   group_name = "my-group"
@@ -28,14 +30,34 @@ resource "sysdig_group_mapping" "my_group" {
 }
 
 ```
+This way, we define a group mapping named "my-group" for a user who will have a standard role in two teams.
+
+### Admin users
+If the group members should assume the Sysdig administrator role the mapping should be created this way
+
+```terraform
+resource "sysdig_group_mapping" "admin" {
+  group_name = "admin"
+  role = "ROLE_TEAM_MANAGER"
+  system_role = "ROLE_CUSTOMER"
+
+  team_map {
+    all_teams = true
+    team_ids = []
+  }
+}
+```
+The name doesn’t necessarily have to be “admin,” it’s just an example. The important aspects are the roles and the team_map
 
 ## Argument Reference
 
 * `group_name` - (Required) The group name to be mapped.
 
 * `role` - (Required) The role that is assigned to the users. It can be a standard role or a custom team role ID.
 
-* `system_role` (Optional) The system role that is assigned to the users.
+* `system_role` (Optional) The system role that is assigned to the users. The supported values are: 
+  * `ROLE_USER` for regular users (Default if not specified) 
+  * `ROLE_CUSTOMER` for admin users
 
 * `team_map` - (Required) Block to define team mapping.