Ensure en is an I18n fallback in all environments

Since `en` is considered as the main fallback for all locales
ensure that it is present in all environments.

Note: Setting `config.i18n.fallbacks` to `true` means use the default locale
which means that if a particular instance is not using an `en` based locale
(the parent `en` locale is automatically derived as a fallback) then `en` will
not be available as a fallback.

config/environments/development.rb

@@ -29,6 +29,8 @@ Openfoodnetwork::Application.configure do
   # Expands the lines which load the assets
   config.assets.debug = false
 
+  config.i18n.fallbacks = [:en]
+
   # Show emails using Letter Opener
   config.action_mailer.delivery_method = :letter_opener
   config.action_mailer.default_url_options = { host: "0.0.0.0:3000" }

config/environments/production.rb

@@ -56,7 +56,7 @@ Openfoodnetwork::Application.configure do
 
   # Enable locale fallbacks for I18n (makes lookups for any locale fall back to
   # the I18n.default_locale when a translation can not be found)
-  config.i18n.fallbacks = [:en]
+  config.i18n.fallbacks = true
 
   # Send deprecation notices to registered listeners
   config.active_support.deprecation = :notify

config/environments/staging.rb

@@ -56,7 +56,7 @@ Openfoodnetwork::Application.configure do
 
   # Enable locale fallbacks for I18n (makes lookups for any locale fall back to
   # the I18n.default_locale when a translation can not be found)
-  config.i18n.fallbacks = true
+  config.i18n.fallbacks = [:en]
 
   # Send deprecation notices to registered listeners
   config.active_support.deprecation = :notify

config/environments/test.rb

@@ -36,6 +36,7 @@ Openfoodnetwork::Application.configure do
   # Tests assume English text on the site.
   config.i18n.default_locale = "en"
   config.i18n.available_locales = ['en', 'es']
+  config.i18n.fallbacks = [:en]
   I18n.locale = config.i18n.locale = config.i18n.default_locale
 
   # Use SQL instead of Active Record's schema dumper when creating the test database.