add CREEP_FILL extrapolation method, needs ESMF PR merged

[raphaeldussin]

once PR esmf-org/esmf#18 is merged (and new ESMPy released?)
add the method to xESMF supported extrapolation methods

[huard]

A new conda build for ESMPy seems to be available.

[raphaeldussin]

yes, it's on my todo list, I want to test and document the several extrapolation methods

[huard]

https://github.com/esmf-org/esmf/releases/tag/ESMF_8_1_0

[raphaeldussin]

@huard I noticed it too! I need to work on documenting the extrapolation methods and make a PR to include the new method. my bandwidth is lower than a dial-up modem right now :(

[huard]

No pressure! I was just noting it for future reference.

[imcslatte]

Hello,

I was wondering if CREEP fill extrapolation would be added to xesmf? It would be a really usefull tool.

Thanks,

Eli