[pholder] add support (#2568 #9067)

* feat: extractor for pholder.com
    Closes #2568
* feat[pholder]: support gallery_id properly and tags
* doc[text.nameext_from_name]: minor typo in docstring

* remove '__init__' & 'request' methods and 'json' import
* use 'text.nameext_from_url' to ensure a 'filename' value
* fix 'imgur' links by disabling auto-Referer
* fix 'data["id"].partition()' call
    'partition' returns 3 elements
* use 'item["_source"]' data directly
* remove unused supportedsites overwrite
* catch all exceptions in '_thumb_resolution'
    fixes "KeyError: 'width'"
* use 'author' name for user folders

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

scripts/supportedsites.py

@@ -153,6 +153,7 @@ CATEGORY_MAP = {
     "nudostarforum"  : "NudoStar Forums",
     "okporn"         : "OK.PORN",
     "paheal"         : "Rule 34",
+    "pholder"        : "pholder",
     "photovogue"     : "PhotoVogue",
     "picstate"       : "PicState",
     "pidgiwiki"      : "PidgiWiki",