Changes
-------
- Bump frontend-platform to bring `intl-imports.js` script
- Move all i18n imports into `src/i18n/index.js` so `intl-imports.js` can
override it with latest translations
- Add `atlas` into `make pull_translations` when `OPENEDX_ATLAS_PULL`
environment variable is set.
- Refactored i18n utils into own file to avoid overwriting them by
atlas
Refs: [FC-0012 project](https://openedx.atlassian.net/l/cp/XGS0iCcQ) implementing Translation Infrastructure OEP-58.
ae1702d182