Update ix.md (prebid#5102)

* Update ix.md

added instream video section

* Update ix.md

added new supported user IDs

* Update ix.md

removed linked as per review comments

* Update ix.md

fixed lint errors

* Update ix.md

fixed link errors

* Update ix.md

added support for merkel user id

dev-docs/bidders/ix.md

@@ -5,7 +5,7 @@ description: Prebid Index Exchange Bidder Adapter
 biddercode: ix
 pbjs: true
 pbs: false
-userIds: identityLink, netId, fabrickId, zeotapIdPlus, uid2, unifiedId, id5Id, lotamePanoramaId, publinkId, hadronId, pubcid, imuid, 33acrossId, nonID
+userIds: idl, netId, fabrickId, zeotapIdPlus, uid2, TDID, id5Id, lotamePanoramaId, publinkId, hadronId, pubcid, utiq, criteoID, euid, imuid, 33acrossId, nonID, pairid, MRKL
 pbs_app_supported: true
 schain_supported: true
 coppa_supported: true
@@ -37,7 +37,8 @@ privacy_sandbox: paapi, topics
   * [Global data](#prebid-fpd-module)
   * [Index bidder-specific data](#index-bidder-specific-fpd-module)
   * [AdUnit-specific data](#adunit-specific-data)
-* [Index's outstream video player](#index-outstream-video-player)
+* [Monetize instream video](#monetize-instream-video)
+* [Index's outstream ad unit](#indexs-outstream-ad-unit) 
 * [Prebid Native configuration](#prebid-native-configuration)
 * [Protected Audience API support](#protected-audience-api-support)
 * [Signal inventory using  external IDs](#signal-inventory-using-external-ids)
@@ -124,18 +125,9 @@ In this configuration, Prebid.js makes a call to Prebid Server and then Prebid S
     ```
 
 6. (Optional) Set up First Party Data (FPD). For more information about the data types we support and the instructions for each option, see the [Set up First Party Data (FPD)](#set-up-first-party-data-fpd) section below.
-7. (Optional) If you want to monetize instream video, you need to enable a cache endpoint in the `[pbjs.setConfig()]` function as follows:
-
-    ```javascript
-    pbjs.setConfig({
-        cache: {
-                url: 'https://prebid.adnxs.com/pbc/v1/cache'
-            }
-    });
-    ```
-
+7. (Optional) If you want to monetize instream video, see the [Monetize instream video](#monetize-instream-video) section below.
 8. (Optional) If you want to monetize outstream video, you can choose among the following options:
-    * Use Index's outstream video player. For more information, see the [Index's outstream video player](#index-outstream-video-player) section below.
+    * Use Index's outstream video player. For more information, see the [Index's outstream ad unit](#indexs-outstream-ad-unit) section below.
     * Use your own outstream video player. For more information, see [Prebid’s documentation on how to show video ads.](/dev-docs/show-outstream-video-ads.html)
 9. (Optional) Configure Prebid Native with Index. For more information, see the [Prebid Native](#prebid-native-configuration) section below. Prebid Native is available from Prebid.js version 7.4.0 or higher.
 
@@ -222,7 +214,23 @@ ortb2Imp: {
 }
 ```
 
-<a id="index-outstream-video-player"></a>
+## Monetize instream video 
+
+Unlike Outstream Video, instream video does not use the Prebid Universal Creative. Instead, video bids provide VAST that Prebid caches to obtain a cache ID that can be retrieved with a URL. The cache ID is passed as a key value to the ad server.  
+
+To monetize instream video, complete the following steps: 
+
+1. Enable a cache endpoint in the `[pbjs.setConfig()]` function as follows:
+
+   ```javascript
+   pbjs.setConfig({ 
+     cache: { 
+             url: 'https://prebid.adnxs.com/pbc/v1/cache' 
+         } 
+   });
+   ```
+
+2. Set up your line items in Google Ad manger by following the instructions in Prebid's [Setting Up Video In GAM](/adops/setting-up-prebid-video-in-dfp.html) documentation. 
 
 ## Index's outstream ad unit