[fansly] add initial support (#4401)

- only posts and creator posts work
- 'home' and 'list' extractors do nothing atm
- needs 'authorization' header as 'token' config value
  to access locked content
- needs yt-dlp to download 1080p videos

gallery_dl/extractor/__init__.py

@@ -56,6 +56,7 @@ modules = [
     "exhentai",
     "facebook",
     "fanbox",
+    "fansly",
     "fantia",
     "fapello",
     "fapachi",