added extractor 'e621'

gallery_dl/extractor/e621.py

@@ -0,0 +1,8 @@
+from .gelbooru import BooruExtractor
+
+class Extractor(BooruExtractor):
+
+    def __init__(self, match, config):
+        BooruExtractor.__init__(self, match, config)
+        self.category = "e621"
+        self.api_url  = "https://e621.net/post/index.xml"