Merge branch 'mrf-silence-2' into 'develop'

MRF silencing alternative solution

See merge request pleroma/pleroma!2820

config/description.exs

@@ -1542,6 +1542,12 @@ config :pleroma, :config_description, [
         description: "List of instances to only accept activities from (except deletes)",
         suggestions: ["example.com", "*.example.com"]
       },
+      %{
+        key: :followers_only,
+        type: {:list, :string},
+        description: "Force posts from the given instances to be visible by followers only",
+        suggestions: ["example.com", "*.example.com"]
+      },
       %{
         key: :report_removal,
         type: {:list, :string},