adding documentation for jixie Id module which is applying for submission into the PrebidJs repo concurrently (#6030)

* as we are adding the prebid-server adaptor and introduced a few extra params , they are added here too
(note: those 3 new params would also reach the headerbid adserver in the case of prebid "clientside HB" too. So all good)

* added quotes around string params

* add jixieId module md file

---------

Co-authored-by: bretg <bgorsline@gmail.com>

Author: jxdeveloper1

dev-docs/modules/userid-submodules/jixie.md

@@ -0,0 +1,49 @@
+---
+layout: userid
+title: Jixie ID
+description: Jixie ID User ID sub-module
+useridmodule: jixieId
+bidRequestUserId: jixieId
+eidsource: jixie.io
+example: '"1111"'
+---
+
+
+The Jixie ID module is specially useful for publishers that will connect with Jixie bidder through PrebidServer adapter feature of PrebidJS and/or for publishers that are unable to integrate with the Jixie ID/event script to still acquire the important Jixie client ID for users. 
+
+For assistance setting up your module, please contact us at <partners.jixie.io>
+
+Add the Jixie ID to your Prebid.js Package with:
+
+```bash
+gulp build --modules=userId,jixieIdSystem
+```
+
+## Jixie ID Registration
+
+Please reach out to [partners.jixie.io](mailto:partners.jixie.io) to request your `accountid`
+
+## Jixie ID Configuration
+
+{: .table .table-bordered .table-striped }
+
+| Param under userSync.userIds[] | Scope | Type | Description | Example |
+| --- | --- | --- | --- | --- |
+| name | Required | String | The name of Module | `"jixieId"` |
+| params | optional | Object | Container of all module params. |  |
+| params.accountid | optional | String | This is your `accountid` as provided by Jixie. | `Mo165qXxxx` |
+
+## DMD ID Example
+
+```javascript
+pbjs.setConfig({
+    userSync: {
+        userIds: [{
+            name: 'jixieId',
+            params: {
+                accountid: 'Mo165qXxxx' // provided to you by Jixie
+            }
+        }]
+    }
+});
+```