Support for AppIndicator badges

[hcldan]

Describe the idea or feature you'd like
I can see that AppIndicators are being fired for some of my applications by using https://extensions.gnome.org/extension/615/appindicator-support/

For example, discord shows me I have unread messages:

But it never shows on the panel icon:

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[charlesg99]

duplicate of #1695