[bilibili] Support new Bangumi URLs (closes #11845)

To reduce complexity, I don't support old Bangumi URLs directly via
_VALID_URL. Instead, I choose to let it go to generic redirection. An
example can be found in #10190:

http://bangumi.bilibili.com/anime/v/40062

youtube_dl/extractor/extractors.py

@@ -103,7 +103,10 @@ from .beatport import BeatportIE
 from .bet import BetIE
 from .bigflix import BigflixIE
 from .bild import BildIE
-from .bilibili import BiliBiliIE
+from .bilibili import (
+    BiliBiliIE,
+    BiliBiliBangumiIE,
+)
 from .biobiochiletv import BioBioChileTVIE
 from .biqle import BIQLEIE
 from .bleacherreport import (