Add prebid server support to rtb stack docs

dev-docs/bidders/rtbstack.md

@@ -8,6 +8,7 @@ aliasCode: admixer
 media_types: banner, video, native
 tcfeu_supported: true
 usp_supported: true
+pbs: true
 schain_supported: true
 gvl_id: 511
 userIds: AdmixerID
@@ -18,7 +19,7 @@ multiformat_supported: will-bid-on-any
 safeframes_ok: true
 ---
 
-#### Bidder Configuration
+### Bidder Configuration
 
 RTB Stack bidder requires bidderURL to be set. Please note that rtbstack bids will not be requested without this config. It must be set before auction starts.
 
@@ -31,13 +32,13 @@ pbjs.setBidderConfig({
 });
 ```
 
-### Bid Params
+#### Bid Params
 
 {: .table .table-bordered .table-striped }
 | Name                | Scope    | Description                                                                                | Example                      | Type     |
 |---------------------|----------|--------------------------------------------------------------------------------------------|------------------------------|----------|
-| `tagId`        | required |The unique identifier of the ad placement. Will be used for comparison of statistics.                             | 51772                        | `int`    |
-| `kvTargeting`       | optional | Key/Value - a pair of the unique values that will be used for the custom targeting option. | {key1: value2, key2: value2} | `object` |
+| `tagId`        | required |The unique identifier of the ad placement. Will be used for comparison of statistics.                             | `51772`                        | `int`    |
+| `kvTargeting`       | optional | Key/Value - a pair of the unique values that will be used for the custom targeting option. | `{key1: value2, key2: value2}` | `object` |
 
 #### Bid Example
 
@@ -52,3 +53,30 @@ pbjs.setBidderConfig({
   }
 }
 ```
+
+### Prebid Server Configuration
+The RTB Stack adapter allows publishers to connect to RTB Stack demand through Prebid Server using server-to-server (S2S) bidding.
+
+#### Bid Params
+
+{: .table .table-bordered .table-striped }
+| Name                | Scope    | Description                                                                                | Example                      | Type     |
+|---------------------|----------|--------------------------------------------------------------------------------------------|------------------------------|----------|
+| `route`             | required | Full RTB Stack route URL used to derive the RTB Stack endpoint. This URL typically includes the region host and query parameters such as client, endpoint, and ssp. | `https://us-adx-example.rtb-stack.com/prebid?client=44e2d241-5051-4b58-8ac6-f17e13732339&ssp=3&endpoint=777`   | `string`    |
+| `tagId`             | required | The unique identifier of the ad placement. Will be used for comparison of statistics.     | `12345` | `string` |
+| `customParams`      | optional | Key/Value - a pair of the unique values that will be used for the custom targeting option.     | `{key1: value2, key2: value2}` | `object` |
+
+#### Bid Example
+
+```js
+{
+  bidder: 'rtbstack',
+  params: {
+    tagId: '12345',
+    route: 'https://us-adx-example.rtb-stack.com/prebid?client=44e2d241-5051-4b58-8ac6-f17e13732339&ssp=3&endpoint=777',
+    customParams: {
+      example: 'test'
+    }
+  }
+}
+```