[Canvas] Add new extractor

youtube_dl/extractor/__init__.py

@@ -86,6 +86,7 @@ from .camdemy import (
 )
 from .canalplus import CanalplusIE
 from .canalc2 import Canalc2IE
+from .canvas import CanvasIE
 from .cbs import CBSIE
 from .cbsnews import CBSNewsIE
 from .cbssports import CBSSportsIE