Mgid RTD module docs (#4081)
Mgid RTD module docs (#4081)

* 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

* Mgid RTD module docs

Co-authored-by: gaudeamus <70d9f9a6f526839e28a66e8ffdace6d879d24e45@mgid.com>
Co-authored-by: Gaudeamus <70d9f9a6f526839e28a66e8ffdace6d879d24e45@gmail.com>
prebid/prebid.github.io,prebid/prebid.github.io,prebid/prebid.github.io