I18N: integrate english translations

Summary/TL;DR

I18N: integrate english translations

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Detailed description

Steps to do the task

• add en locales
• update config to allow either french or english
  • https://gitlab.com/Misakey/js-common/blob/master/packages/ui/src/i18n.js#L23
  • https://www.i18next.com/overview/configuration-options
• do not force french anymore in config

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💥 🚨 Breaking changes

English navigators should then display english translations