added coopSync option to s2sConfig (#2743)

dev-docs/publisher-api-reference.md

@@ -1853,6 +1853,7 @@ The `s2sConfig` properties:
 | `endpoint` | Required | URL | Defines the auction endpoint for the Prebid Server cluster |
 | `syncEndpoint` | Required | URL | Defines the cookie_sync endpoint for the Prebid Server cluster |
 | `userSyncLimit` | Optional | Integer | Max number of userSync URLs that can be executed by Prebid Server cookie_sync per request.  If not defined, PBS will execute all userSync URLs included in the request. |
+| `coopSync` | Optional | Boolean | Whether or not PBS is allowed to perform "cooperative syncing" for bidders not on this page. Publishers help each other improve match rates by allowing this. Default is true. Supported in PBS-Java only. |
 | `defaultTtl` | Optional | Integer | Configures the default TTL in the Prebid Server adapter to use when Prebid Server does not return a bid TTL - 60 if not set |
 | `adapterOptions` | Optional | Object | Arguments will be added to resulting OpenRTB payload to Prebid Server in every impression object at request.imp[].ext.BIDDER. See the example above. |
 | `extPrebid` | Optional | Object | Arguments will be added to resulting OpenRTB payload to Prebid Server in request.ext.prebid. See the examples below. |