add suim docs (#6040)

Author: rororo

dev-docs/bidders/suim.md

@@ -0,0 +1,20 @@
+---
+layout: bidder
+title: Suim
+description: Prebid Suim Bidder Adapter
+pbjs: true
+biddercode: suim
+media_types: banner
+sidebarType: 1
+---
+
+Note:
+The Suim Bidding adapter requires setup before beginning.
+For more information, visit [Suim website](https://suim.co.jp/).
+
+### Bid parameters
+
+{: .table .table-bordered .table-striped }
+| Name          | Scope    | Description                  | Example                         | Type     |
+|---------------|----------|------------------------------|---------------------------------|----------|
+| `ad_space_id` | required | Ad space ID provided by Suim | `'101hw085aphx9qdttwgdnm5q5b8'` | `string` |