Add French-English translation

[tedspare]

• We'll use the external internationalization ("i18n") library react-i18next
• To get started, create a file src/i18n/index.js with an object mapping keys to EN and FR phrases like this:

const resources = {
  en: {
    translation: {
      "welcomeDialogTitle": "Welcome to the MU Open-Air Museum"
    }
  },
  fr: {
    translation: {
      "welcomeDialogTitle": "Bienvenue au musée de plein air MU"
    }
  }
};

• Inside of components with user-readable text, import the i18n hook like this:

import { useTranslation } from 'react-i18next';

function SomeComponent () {
  const { t } = useTranslation();
  return <div>{t("welcomeDialogTitle")}</div>
}