[myhentaigallery] update and fix extraction (#1001)

- extract more metadata
- match "/show/" URLs
- complete test results
- fix missing images for lines starting with " <img"
- fix missing comma in supportedsites.py

scripts/supportedsites.py

@@ -60,7 +60,7 @@ CATEGORY_MAP = {
     "mangapark"      : "MangaPark",
     "mangastream"    : "Manga Stream",
     "mastodon.social": "mastodon.social",
-    "myhentaigallery": "My Hentai Gallery"
+    "myhentaigallery": "My Hentai Gallery",
     "myportfolio"    : "Adobe Portfolio",
     "nhentai"        : "nhentai",
     "nijie"          : "nijie",