Update firstPartyData.md with app.content.data example (#3299)
Update firstPartyData.md with app.content.data example (#3299)

* Update firstPartyData.md

* Update firstPartyData.md

* fixing indentation

Co-authored-by: bretg <9df09da23577b88db5b6b8911d0635d4f870e78e@gmail.com>
prebid/prebid.github.io,prebid/prebid.github.io,prebid/prebid.github.io