Add option to opt out of search engines on public profile/status pages (#4199)

app/views/follower_accounts/index.html.haml

@@ -2,6 +2,9 @@
   = t('accounts.people_who_follow', name: display_name(@account))
 
 - content_for :header_tags do
+  - if @account.user&.setting_noindex
+    %meta{ name: 'robots', content: 'noindex' }/
+
   = render 'accounts/og', account: @account, url: account_followers_url(@account, only_path: false)
 
 = render 'accounts/header', account: @account