Add docs for Subdomain resource

Author: emichaeli

website/docs/r/subdomain.html.markdown

@@ -0,0 +1,30 @@
+---
+layout: "sumologic"
+page_title: "SumoLogic: sumologic_subdomain"
+description: |-
+  Provides a Sumologic Subdomain
+---
+
+# sumologic_lookup_table
+Provides a [Sumologic Subdomain][1].
+
+## Example Usage
+```hcl
+resource "sumologic_subdomain" "exampleSubdomain" {
+    subdomain = "my-company"
+}
+```
+
+## Argument reference
+
+The following arguments are supported:
+
+- `subdomain` - (Required) The subdomain.
+
+## Attributes reference
+
+The following attributes are exported:
+
+- `id` - Unique identifier for the subdomain.
+
+[1]: https://help.sumologic.com/Manage/01Account_Usage/05Manage_Organization#change-account-subdomain