[fitnakedgirls] add support (#8671)

* [fitnakedgirls] add extractor

Add support for fitnakedgirls.com:
- Photo galleries (/photos/gallery/)
- Category pages (/photos/gallery/category/)
- Tag pages (/photos/tag/)
- Video posts (/videos/)
- Blog posts (/fitblog/)

Handles both newer (wp-block-image) and older (size-large) templates.

* simplify & fix

- use '_extract_title' method
- move '_pagination' into base class
- update 'FitnakedgirlsTagExtractor' pattern

* update docs/supportedsites

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Co-authored-by: Mike Fährmann <mike_faehrmann@web.de>

gallery_dl/extractor/__init__.py

@@ -68,6 +68,7 @@ modules = [
     "fapello",
     "fapachi",
     "fikfap",
+    "fitnakedgirls",
     "flickr",
     "furaffinity",
     "furry34",