Add "chunk dims" text field for load state chunk dims

[evamaxfield]

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Use Case

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Allow for the parameterization of chunk dimensions on scene / image selection.

Solution

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With the addition of #27 (and major credit to @psobolewskiPhD I think it's possible to add a chunk dims text field that allows the user to specify which dimensions to chunk by, we then read that string prior to loading the scene / requesting the xarray_*_data.

Alternatives

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