fix: broken link to AMO button image, we now serve the image ourselves

Author: ErikBjare

downloads.pug

@@ -45,7 +45,7 @@ article.container
 
   div
     a(href="https://addons.mozilla.org/en-US/firefox/addon/aw-watcher-web/").mr-2
-      img(src="https://addons.cdn.mozilla.net/static/img/addons-buttons/AMO-button_1.png")
+      img(src="/img/AMO-get-the-addon-178x60px.png")
 
     a(href="https://chrome.google.com/webstore/detail/nglaklhklhcoonedhgnpgddginnjdadi/")
       img(src="/img/ChromeWebStore_BadgeWBorder_v2_206x58.png", height="58")