add comment to .env.erb file

deploy/.env.erb

@@ -1,8 +1,13 @@
+<%#
+This file is used by Kamal to generate the `deploy/.env` file when running `kamal envify`
+It is a Ruby 'ERB' template, so you can use Ruby code in it.
+See https://fireapp.kkbox.com/doc/tutorial_2.html for more information.
+%>
 <% `op signin --account dimagi.1password.com --raw` %>
 <% if $?.exitstatus == 0 %>
 <% vars = YAML.load(`op item get --vault "CommCare Connect" "Connect Secrets" --fields type=string,type=concealed`) %>
 <% for var in vars %><% if var.key?("Value") %><% if var["Value"].kind_of?(Array) %>
 <%= var['Label'] %>=<%= var['Value'].join(',') %>
 <% else %><%= var['Label'] %>=<%= var['Value'] %>
 <% end %><% end %><% end %>
-<% else raise ArgumentError, "Error getting values from 1Password" end %>
+<% else raise ArgumentError, "Error getting values from 1Password. Try sign in." end %>