Fixes export option in H5Web

H5Web was not able to export data into npy/csv files. This adds the necessary client code to make it work within Nomad. H5Web would just open the path in a new window and this didn't have our Authorization header. With the new code, it downloads the file using axios and emulates a click on an HREF tag. All of this is done silently by the H5Web component.

@josma This should fix it. Please have a look if it works for you. I'll spin up an instance of this branch for you to test.