Update README.md

Author: puddingspudding

README.md

@@ -4,7 +4,7 @@
     <img src="https://storage.googleapis.com/chrome-gcs-uploader.appspot.com/image/WlD8wC6g8khYWPJUsQceQkhXSlv1/mPGKYBIR2uCP0ApchDXE.png" height="60px"/>
 </a>
 <a href="https://addons.mozilla.org/firefox/addon/persistent-video-audio-volume/?src=external-github" target="_blank">
-    <img src="https://addons.cdn.mozilla.net/static/img/addons-buttons/AMO-button_1.png" height="60px"/>
+    <img src="https://blog.mozilla.org/addons/files/2015/11/get-the-addon.png" height="60px"/>
 </a>
 <a href="https://chrome.google.com/webstore/detail/persistent-video-volume/ppoliijncpdcgddmfibmgnjhegceaadj" target="_blank">
     <img src="https://github.com/puddingspudding/persistent-video-volume/raw/release-0.11.0/brave-logotype-full-color.png" height="60px"/>