Since it's using `require` to get the localisation strings, check if the error is `MODULE_NOT_FOUND` before moving on – because if it isn't, then there is an unknown error that should be thrown. Thanks @rschamp for the suggestion!
Before we were using glob, which was about to start failing on subdirectories in views (which we started using in `conference`). Instead of searching for `l10n.json`, it seemed more appropriate to instead look for localization by using the configured pages that need to be localized.
1. checks the localization for a few reference languages for the nav bar
2. for our localized pages (splash, about, wedo2), it checks to see that there are locale strings, whether or not they're english (to make sure at least something is on the page).
This moves all locale/translation building to a dependency, `scratch-www-intl-loader`, as well as tests associated with it. Also gets rid of the `make translations` step.
