README is out of date

[masonproffitt]

The README only mentions func_adl.xAOD (an outdated name for the xAOD backend) for running on ServiceX and func_adl.xAOD.backend (does this one even work anymore?) for running locally, so it's missing the uproot backend, and I think func_adl_servicex is the actual package you'd want for running on ServiceX. There are also no links to any of these or ServiceX, nor the documentation mentioned, which I guess is https://github.com/iris-hep/func_adl/blob/master/documentation.md, but that also seems out of date since it metions ServiceXDatasetSource (I don't think this exists anywhere anymore?).

Considering this is the FuncADL repository, this README seems like the most important one to have up to date.