FEATURE: Allow pausing animated images in posts (#12795)

Co-authored-by: Jarek Radosz <jradosz@gmail.com>

spec/components/cooked_post_processor_spec.rb

@@ -973,7 +973,7 @@ describe CookedPostProcessor do
       expect(doc.css('img').first['srcset']).to_not eq(nil)
     end
 
-    it "does not optimize animated images" do
+    it "does not optimize animated images but adds a class so animated images can be identified" do
       upload.update!(animated: true)
       post = Fabricate(:post, raw: "![image|1024x768, 50%](#{upload.short_url})")
 
@@ -984,6 +984,7 @@ describe CookedPostProcessor do
       expect(doc.css('.lightbox-wrapper').size).to eq(1)
       expect(doc.css('img').first['src']).to include(upload.url)
       expect(doc.css('img').first['srcset']).to eq(nil)
+      expect(doc.css('img.animated').size).to eq(1)
     end
 
     it "optimizes images in quotes" do