PBJS: document new option for RTD submodules (prebid#4467)

dev-docs/add-rtd-submodule.md

@@ -90,13 +90,14 @@ In order to let RTD-core know where to find the functions in your sub-module, cr
 |  param name | type  | Scope | Description | Params |
 | :------------ | :------------ | :------ | :------ | :------ |
 | name  | string  | required | must match the name provided by the publisher in the on-page config | n/a |
-|  init | function | required | defines the function that does any auction-level initialization required | config, userConsent |
-|  getTargetingData  | function | optional | defines a function that provides ad server targeting data to RTD-core | adUnitArray, config, userConsent |
-|  getBidRequestData  | function | optional | defines a function that provides bid request data to RTD-core | reqBidsConfigObj, callback, config, userConsent  |
-|  onAuctionInitEvent | function | optional | listens to the AUCTION_INIT event and calls a sub-module function that lets it inspect and/or update the auction | auctionDetails, config, userConsent |
-|  onAuctionEndEvent | function |optional | listens to the AUCTION_END event and calls a sub-module function that lets it know when auction is done | auctionDetails, config, userConsent |
-|  onBidRequestEvent | function |optional | listens to the BID_REQUESTED event and calls a sub-module function that lets it know when a bid is about to be requested | bidRequest, config, userConsent |
-|  onBidResponseEvent | function |optional | listens to the BID_RESPONSE event and calls a sub-module function that lets it know when a bid response has been collected | bidResponse, config, userConsent |
+| gvlid | number | optional | global vendor list ID for your submodule | n/a | 
+| init | function | required | defines the function that does any auction-level initialization required | config, userConsent |
+| getTargetingData  | function | optional | defines a function that provides ad server targeting data to RTD-core | adUnitArray, config, userConsent |
+| getBidRequestData  | function | optional | defines a function that provides bid request data to RTD-core | reqBidsConfigObj, callback, config, userConsent  |
+| onAuctionInitEvent | function | optional | listens to the AUCTION_INIT event and calls a sub-module function that lets it inspect and/or update the auction | auctionDetails, config, userConsent |
+| onAuctionEndEvent | function |optional | listens to the AUCTION_END event and calls a sub-module function that lets it know when auction is done | auctionDetails, config, userConsent |
+| onBidRequestEvent | function |optional | listens to the BID_REQUESTED event and calls a sub-module function that lets it know when a bid is about to be requested | bidRequest, config, userConsent |
+| onBidResponseEvent | function |optional | listens to the BID_RESPONSE event and calls a sub-module function that lets it know when a bid response has been collected | bidResponse, config, userConsent |
 
 For example:
 {% highlight text %}