[shimmie2] add generic extractors for Shimmie2 sites (#3734)

add support for
- loudbooru.com       (#3734)
- booru.cavemanon.xyz (#3734)
- giantessbooru.com   (#943)
- tentaclerape.net

docs/supportedsites.md

@@ -541,12 +541,6 @@ Consider all sites to be NSFW unless otherwise known.
     <td>Albums, Channels</td>
     <td>Supported</td>
 </tr>
-<tr>
-    <td>meme.museum</td>
-    <td>https://meme.museum/</td>
-    <td>Posts, Tag Searches</td>
-    <td></td>
-</tr>
 <tr>
     <td>My Hentai Gallery</td>
     <td>https://myhentaigallery.com/</td>
@@ -1266,6 +1260,40 @@ Consider all sites to be NSFW unless otherwise known.
     <td></td>
 </tr>
 
+<tr>
+    <td colspan="4"><strong>Shimmie2 Instances</strong></td>
+</tr>
+<tr>
+    <td>meme.museum</td>
+    <td>https://meme.museum/</td>
+    <td>Posts, Tag Searches</td>
+    <td></td>
+</tr>
+<tr>
+    <td>Loudbooru</td>
+    <td>https://loudbooru.com/</td>
+    <td>Posts, Tag Searches</td>
+    <td></td>
+</tr>
+<tr>
+    <td>Giantessbooru</td>
+    <td>https://giantessbooru.com/</td>
+    <td>Posts, Tag Searches</td>
+    <td></td>
+</tr>
+<tr>
+    <td>Tentaclerape</td>
+    <td>https://tentaclerape.net/</td>
+    <td>Posts, Tag Searches</td>
+    <td></td>
+</tr>
+<tr>
+    <td>Cavemanon</td>
+    <td>https://booru.cavemanon.xyz/</td>
+    <td>Posts, Tag Searches</td>
+    <td></td>
+</tr>
+
 <tr>
     <td colspan="4"><strong>szurubooru Instances</strong></td>
 </tr>