[aftenposten] Add extractor (Closes #4863)

youtube_dl/extractor/__init__.py

@@ -6,6 +6,7 @@ from .academicearth import AcademicEarthCourseIE
 from .addanime import AddAnimeIE
 from .adobetv import AdobeTVIE
 from .adultswim import AdultSwimIE
+from .aftenposten import AftenpostenIE
 from .aftonbladet import AftonbladetIE
 from .aljazeera import AlJazeeraIE
 from .alphaporno import AlphaPornoIE