[extractors] Add hrti:playlist import

youtube_dl/extractor/extractors.py

@@ -326,7 +326,10 @@ from .hotnewhiphop import HotNewHipHopIE
 from .hotstar import HotStarIE
 from .howcast import HowcastIE
 from .howstuffworks import HowStuffWorksIE
-from .hrti import HRTiIE
+from .hrti import (
+    HRTiIE,
+    HRTiPlaylistIE,
+)
 from .huffpost import HuffPostIE
 from .hypem import HypemIE
 from .iconosquare import IconosquareIE