copy assets rollup module

[atherdon]

at package.json we have a module, that should copy files(if needed) while building code to es6 version. and before few last weeks, this module was outdated and not copying our files.
My idea was: move away data folder outside of src - because at that folder only tests are not static. and have maybe another folder for generated json as well. and when we'll run a build, data from both static and generated jsons will be merged inside of dist folder, that actually are publishing at npm

[atherdon]

@etg624 I think this will be an interesting task for you. Some things were changed for the last month, but let's have a discussion here and figure out how to do it