Nan threshold for conservative regridding (continuation of #39)

[BSchilperoort]

Continuation of #39

• Corrected the typing of the modified routines
• Added a demo notebook (based on the example from NaN threshold for conservative method #39)
• Added @slevang to contributors

[BSchilperoort]

@slevang I tidied up some things and added additional documentation to your PR. Could you have a (quick) look at this? If not just let me know and I merge it as-is

[slevang]

Thanks, and good timing! I finally have some free time this week and was planning to finish this up.

I did want to revisit the way I implemented the NaN thresholding across dimensions following this comment, and maybe try being more explicit by having the user pass a mask.

[BSchilperoort]

Thanks, and good timing! I finally have some free time this week and was planning to finish this up.

I did want to revisit the way I implemented the NaN thresholding across dimensions following this comment, and maybe try being more explicit by having the user pass a mask.

Great! Maybe it's better to merge this PR first, so you can work in a clean branch. That would be easier to review.

I did move those comments to #42 already

[slevang]

That works for me, thanks for finishing up the typing, etc. I can work on any small follow ups in another PR. This already has quite a lot of changes.