[ie/FlexTV] Add extractor (#9178)

Closes #9175
Authored by: DmitryScaletta

yt_dlp/extractor/_extractors.py

@@ -618,6 +618,7 @@ from .filmon import (
 from .filmweb import FilmwebIE
 from .firsttv import FirstTVIE
 from .fivetv import FiveTVIE
+from .flextv import FlexTVIE
 from .flickr import FlickrIE
 from .floatplane import (
     FloatplaneIE,