Resolve "Add translation support en/fr"

Closes #21

name: Feature about: New features or wider changes,

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Description

Supports automatic translation based on the browser's language

• default is english, french is supported
• all strings are in assets' forlder json files
• files loaded, id of element piped to translate service

How to test

• Launch both frontend and backend (required for authentication)
• access with browsers using english or franch
• verifiy that text is in the appropriate language

Misc

Based on ngx-translate, the main translation package for Angular. Complete tutorial is available here: https://www.codeandweb.com/babeledit/tutorials/how-to-translate-your-angular8-app-with-ngx-translate

Changelog

• Added internationalization with fr/en supported