Update directlink.py with additional file exts. (#30)

Add WebP, still not that common, but it's increasing.
Add 3rd JPEG variant (https://en.wikipedia.org/wiki/JPEG#JPEG_filename_extensions)
Never seen JFIF in the wild, would probably be overkill.
Extend Ogg formats (https://en.wikipedia.org/wiki/Ogg; https://wiki.xiph.org/MIME_Types_and_File_Extensions)

gallery_dl/extractor/directlink.py

@@ -16,7 +16,7 @@ class DirectlinkExtractor(Extractor):
     """Extractor for direct links to images"""
     category = "directlink"
     filename_fmt = "{domain}/{path}"
-    pattern = [r"https?://([^/]+)/([^?&#]+\.(?:jpe?g|png|gif|webm|mp4|ogg))"]
+    pattern = [r"https?://([^/]+)/([^?&#]+\.(?:jpe?g?|png|gif|webp|webm|mp4|mkv|ogg|ogm|ogv|opus))"]
     test = [(("https://photos.smugmug.com/The-World/Hawaii/"
               "i-SWz2K6n/2/X3/IMG_0311-X3.jpg"), {
         "url": "32ee1045881e17ef3f13a9958595afa42421ec6c",