fix images in rss feed

- escape alt text
- add "full image hidden" message if it is

make-pages/RSS.hs

@@ -87,16 +87,21 @@ makeItem root prefix nsfw path info@(Info {title}) = [b|
     Artist name (Just url) -> [b|<p>by <a href="$url">$name</a>|]
   desc = makeDesc $ descFor nsfw info
 
-  image = case previewImage info of
-    Just (PFull img) -> figure img.desc $ pageFile img
+  preview = previewImage info 
+  image = case preview of
+    Just (PFull img) -> figure (escAttr img.desc) $ pageFile img
     Just (PThumb th) -> figure "full image hidden" $ thumbFile th
     Nothing          -> ""
+  msg = case preview of
+    Just (PThumb _) -> "<p>(full image hidden; open to see)</p>"
+    _               -> "" :: Text
   figure alt p = [b|
       <figure aria-describedby=mainimg>
         <a href="$link">
           <img id=mainimg src="$link/$p" alt="$alt" title="$alt">
         </a>
       </figure>
+      $msg
     |]
 
 makeDesc :: Desc -> Builder