Deprecating indigo footer package & use of plugin slot to override it breaks the footer overrides using plugin slot for other users

[Faraz32123]

Indigo Footer package was deprecated in this PR(#181), and this PR used plugin slot to override the default footer.
But the use of plugin slot broke the footer override for those users who were already using plugin slots as mentioned here.

I suggested a solution here, using this users can use their custom footer using plugin slots while still keeping the indigo plugin enabled.