Add all English translations

[thibaudgg]

After applying this diff:

diff --git a/lib/tasks/locales.rake b/lib/tasks/locales.rake
index 8daa25de..3beabf24 100644
--- a/lib/tasks/locales.rake
+++ b/lib/tasks/locales.rake
@@ -17,7 +17,6 @@ namespace :locales do
 
   desc "List not yet translated keys"
   task missing: :environment do
-    locales = %w[de fr it]
     translations = load_translations_from_config
     all_keys = translations.flat_map { |l, k| list_all_keys(k) }.uniq.compact
     missing_keys = []
@@ -126,6 +125,6 @@ namespace :locales do
   end
 
   def used_locales
-    I18n.available_locales.sort - [ :en ]
+    I18n.available_locales.sort
   end
 end

All the translations reported as missing by bin/rails locales:missing should be added in all the locales files located in config/locales/*.yml. At the end bin/rails locales:missing should have no output, and bin/rails locales:verify should print Locales passed format verification..

The existing French, German, and Italian translations in config/locales/*.yml should be used as context to add all the _en: new translation lines.