is there a MPP internationalization library? something like gettext maybe? If not, who would fancy to help implementing it as open source library?

I can help because I'm interested in it.

hi 🙂 for mobile development (ios & android) we implement this lib - https://github.com/icerockdev/moko-resources on this or next week we add english readme, full sample and next add gradle plugin to generate MR expect/actual class from some universal xmls

Does it also support localization?

yes, it support localization (i add sample today), localization based on mobile OS logic (by android localization resources & ios). we have not js in plan. but if you add this support - it be cool 🙂

Where can I find the example? (I don't see it in the Readme)

in sample directory. for now readme not updated, later it will be improved and i notify about in in this thread