[NFR] Add ADIOS to available backends

[n01r]

Hey there! :)

Would there be any private branches be lying around somewhere that also update ADIOS1/2 files?

[ax3l]

Not yet, but the implementation with ADIOS' numpy bindings would go into these locations:
https://github.com/openPMD/openPMD-updater/tree/master/openpmd_updater/backends

Note that openPMD 2.0.0 is not yet finalized, so you should not yet need the updater.