Ask for a post's images without a referrer

jeffgeerling.com answers 403 to an image request whose Referer is another
site, so his posts showed a broken image on iOS and the alt text on desktop.
The sanitiser now gives every <img> referrerpolicy="no-referrer".

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

CHANGELOG.md

@@ -42,6 +42,8 @@ The long form, with what was wrong before and how it was found, is in
   their own, and on white for an iPhone's home screen.
 - The file icon of an item not yet downloaded sits level with the rest of its row, instead of
   higher than a downloaded one's.
+- Images in posts from sites that refuse images to other sites' pages, such as Jeff Geerling's,
+  now show: ipx asks for them without saying it is the page showing them.
 - An item you open stays read. A list refresh that crossed with marking it read could put its
   unread dot back until the next refresh.
 - On the Unread tab, the item you were reading leaves the list as soon as you move to the next