New Bidder Docs: Realry (#6599)

* Add Realry bidder docs (companion to prebid-server#4813)

* Realry bidder docs: enable pbjs (companion to Prebid.js#14997)

* fix: bump bidder doc headings to h2 (MD001)

* Update dev-docs/bidders/realry.md

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Co-authored-by: Muki Seiler <muuki88@users.noreply.github.com>