Caused some cascade issues where you'd see default fonts in components (i.e. serif). This is only for the playground as, I imagine, in scratch-3.0 this font style would be inherited.
* Added .tx configuation to be able to send source strings to transifex
* added dependency on scratch-l10n 2.x, and removed everything related to generating the l10n messages locally
* updated playground intl reducer to use paint messages from l10n package