chore: allow image referencing from the Mixxx GH organisation

Author: acolombier

netlify.toml

@@ -49,4 +49,4 @@
  for = "/news/*"
  [headers.values]
    # Additionally allow YouTube/Discourse frames and scripts
-    Content-Security-Policy = "default-src 'self'; style-src 'self' 'unsafe-inline'; script-src 'self' 'sha256-UPkidoMErzWw1gW/eY4LhAi9ZkPch3PP31d6KQoJ6Yc='  'sha256-G40wI6OaLZXCtrb02xUq1H1kEVWjstzoQ0FXKwsWxPw='	https://mixxx.discourse.group/javascripts/embed.js *.discourse-cdn.com; frame-src 'self' https://www.youtube-nocookie.com https://mixxx.discourse.group ; img-src 'self' https://i.ytimg.com ; connect-src 'self' https://mixxx.discourse.group https://*.discourse-cdn.com"
+    Content-Security-Policy = "default-src 'self'; style-src 'self' 'unsafe-inline'; script-src 'self' 'sha256-UPkidoMErzWw1gW/eY4LhAi9ZkPch3PP31d6KQoJ6Yc='  'sha256-G40wI6OaLZXCtrb02xUq1H1kEVWjstzoQ0FXKwsWxPw='	https://mixxx.discourse.group/javascripts/embed.js *.discourse-cdn.com; frame-src 'self' https://www.youtube-nocookie.com https://mixxx.discourse.group ; img-src 'self' https://i.ytimg.com https://github.com/mixxxdj ; connect-src 'self' https://mixxx.discourse.group https://*.discourse-cdn.com"