create dir before writing to netcdf

[aurelienfalco]

Minor fix to avoid having to create the directory by hand when creating a netcdf

[codecov]

Codecov Report

❌ Patch coverage is 34.48276% with 19 lines in your changes missing coverage. Please review.
✅ Project coverage is 82.90%. Comparing base (9a572a9) to head (661521a).

Files with missing lines	Patch %	Lines
xdas/core/routines.py	29.16%	17 Missing ⚠️
xdas/core/dataarray.py	66.66%	1 Missing ⚠️
xdas/core/datacollection.py	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##              dev      #51      +/-   ##
==========================================
- Coverage   83.21%   82.90%   -0.31%     
==========================================
  Files          43       43              
  Lines        4569     4598      +29     
==========================================
+ Hits         3802     3812      +10     
- Misses        767      786      +19     

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[atrabattoni]

this pull request is linked to the wrong branch. I close it to reopen it.

[atrabattoni]

Re-open as #56.

[atrabattoni]

Re-open as #56.