Add information about how to opt-in to the directory on the directory (#9834)

Fix #9833

app/views/directories/index.html.haml

@@ -41,8 +41,22 @@
       = paginate @accounts
 
   .column-1
-    - if @tags.empty?
-      .nothing-here.nothing-here--flexible
+    - if user_signed_in?
+      .box-widget.notice-widget
+        - if current_account.discoverable?
+          - if current_account.followers_count < Account::MIN_FOLLOWERS_DISCOVERY
+            %p= t('directories.enabled_but_waiting', min_followers: Account::MIN_FOLLOWERS_DISCOVERY)
+          - else
+            %p= t('directories.enabled')
+        - else
+          %p= t('directories.how_to_enable')
+
+          = link_to settings_profile_path do
+            = t('settings.edit_profile')
+            = fa_icon 'chevron-right fw'
+
+    - if @tags.empty? && !user_signed_in?
+      .nothing-here
     - else
       - @tags.each do |tag|
         .directory__tag{ class: tag.id == @tag&.id ? 'active' : nil }