Feature request: Add support for temperatures

[shimwell]

Thanks for making this package Paul

I've been trying to make use of endf.IncidentNeutron instead of openmc.IncidentNeutron for a plotting package I'm working on.

The first feature that appears to be different is the temperature attribute.

import openmc
openmc_neutron = openmc.data.IncidentNeutron.from_ace('neutron_file/Li/006/lib/endf/Li006-n.ace')
openmc_neutron.temperatures
>>>['293K']

import endf
endf_neutron = endf.IncidentNeutron.from_ace('neutron_file/Li/006/lib/endf/Li006-n.ace')
endf_neutron.temperatures
>>> AttributeError: module 'endf' has no attribute 'temperature'. Did you mean: 'temperature_str'?

Just wondering if adding temperature is on the roadmap

[shimwell]

looks like one can access the temperatures with this code

endf_neutron = endf.IncidentNeutron.from_ace('neutron_file/Li/006/lib/endf/Li006-n.ace')
reactions=endf_neutron.reactions[1]
temperatures=list(reactions.xs.keys())

So perhaps we could just add a getter to the IncidentNeutron class

[shimwell]

If we do add tempertures then we could perhaps also sneak in IncidentNeutron.kTs which is in the openmc.IncidentNeutron and is the temperture in eV

Also openmc.IncidentNeutron.energy makes use of temperatures for the keys