Added a spatialdata-io mirror

[quentinblampey]

Simple mirror so that spatialdata.io.xenium will call spatialdata_io.xenium if spatialdata-io is installed.

If not installed, it raises an error only when calling spatialdata.io.xenium, while spatialdata.io itself will not raise anything.

[codecov]

Codecov Report

Attention: Patch coverage is 90.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 91.84%. Comparing base (27bb4a7) to head (021eb8c).
Report is 9 commits behind head on main.

Files with missing lines	Patch %	Lines
src/spatialdata/_accessors.py	88.88%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #778      +/-   ##
==========================================
- Coverage   91.89%   91.84%   -0.05%     
==========================================
  Files          45       46       +1     
  Lines        6919     6895      -24     
==========================================
- Hits         6358     6333      -25     
- Misses        561      562       +1     

Files with missing lines	Coverage Δ
src/spatialdata/__init__.py	96.42% <100.00%> (+0.13%)	⬆️
src/spatialdata/_accessors.py	88.88% <88.88%> (ø)

... and 29 files with indirect coverage changes