Add support for path definition

[Adam Kadlec]

I'm trying to use it with nativescript and it is using different folder: app instead of src
It would be good to be able to specify source files folder, because ui of the plugin crashes:

(node:2124) UnhandledPromiseRejectionWarning: Error: ENOENT: no such file or directory, scandir 'C:\xxx\yyy\native-app/src/locales'