A series premiering in eight parts Friday on Netflix. Then there’s Lady Whistledown, skulking in the shadows, ruining lives with a flourish of her pen. When are we going to learn her identity? Those references will mean nothing if you haven’t read Julia Quinn’s popular “Bridgerton” books but after you’ve watched the first few episodes of the Netflix serial bearing the same title, the names of the various Bridgertons and Featheringtons and other assorted characters will be as familiar to you as the Dowager Countess of Grantham and Mr. Bates et al. were to “Downton Abbey” fans.