Add prebid server support to rtb stack docs (#6464)

* Add admixerwl alias for admixerBidAdapter.

* Specify multiformat_supported and safeframes_ok for admixerwl adapter.

* add Prebid Server Support docs to rtb stack

* fix bare examples

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Co-authored-by: Yaroslav Masenko <intgr-user@admixer.ua>
Co-authored-by: AdmixerTech <35560933+AdmixerTech@users.noreply.github.com>
Co-authored-by: Daria Boyko <dariaboiko03@gmail.com>