[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

---------

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

docs/supportedsites.md

@@ -349,6 +349,12 @@ Consider all listed sites to potentially be NSFW.
     <td>Posts, User Profiles</td>
     <td></td>
 </tr>
+<tr id="fitnakedgirls" title="fitnakedgirls">
+    <td>FitNakedGirls</td>
+    <td>https://fitnakedgirls.com/</td>
+    <td>Blogs, Categories, Galleries, Tag Searches, Videos</td>
+    <td></td>
+</tr>
 <tr id="flickr" title="flickr">
     <td>Flickr</td>
     <td>https://www.flickr.com/</td>