[mgid] remove placementId from integration code samples  (#1481)
[mgid] remove placementId from integration code samples  (#1481)

* native support & some optional params added

* native support & some optional params added

* native support & some optional params added

* make placementId optional

* update media types with native support

* remove optional placementId from integration code samples

prebid/prebid.github.io,sonobi/prebid.github.io,sonobi/prebid.github.io,prebid/prebid.github.io,sonobi/prebid.github.io,prebid/prebid.github.io