Added Windows script for langage generation (#212)

frontend/scripts/generate_language_files.cmd

@@ -0,0 +1,4 @@
+echo 'Generating language files'
+cd app_flowy
+
+flutter pub run easy_localization:generate -S assets/translations/ && flutter pub run easy_localization:generate -f keys -o locale_keys.g.dart -S assets/translations/