[wikimedia] generalize (#1443)

- support mediawiki.org
- support mariowiki.com (#3660)

- combine code into a single extractor
  (use prefix as subcategory)
- handle non-wiki instances
- unescape titles

scripts/supportedsites.py

@@ -88,7 +88,9 @@ CATEGORY_MAP = {
     "mangapark"      : "MangaPark",
     "mangaread"      : "MangaRead",
     "mangasee"       : "MangaSee",
+    "mariowiki"      : "Super Mario Wiki",
     "mastodon.social": "mastodon.social",
+    "mediawiki"      : "MediaWiki",
     "micmicidol"     : "MIC MIC IDOL",
     "myhentaigallery": "My Hentai Gallery",
     "myportfolio"    : "Adobe Portfolio",