extract shape of full-resolution image, estimate visium pixel size

[ghaith-mq]

This pull request was created during the TheisLab Hackathon 2024 as part of a project to develop a cloud-based Spatial-DB. The primary goal is to ensure that when users upload spatial datasets to the database, they meet predefined quality and consistency standards.

To achieve this, we’ve introduced new functionality that:

• Estimates pixel size (in micrometers) from Visium spatial transcriptomics data.

• Extracts the image shape of the full-resolution tissue image.

These enhancements are critical for maintaining consistency when integrating spatial datasets from different sources, ensuring that users upload the correct full-resolution image and that spatial data is properly scaled for downstream analysis.
Inspired by Hest1k codebase

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 16.36364% with 46 lines in your changes missing coverage. Please review.

Project coverage is 44.75%. Comparing base (cff4896) to head (450bcd2).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
src/spatialdata_io/readers/visium.py	16.36%	46 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #219      +/-   ##
==========================================
- Coverage   45.50%   44.75%   -0.76%     
==========================================
  Files          22       22              
  Lines        2149     2203      +54     
==========================================
+ Hits          978      986       +8     
- Misses       1171     1217      +46     

Files with missing lines	Coverage Δ
src/spatialdata_io/readers/visium.py	18.18% <16.36%> (-1.50%)	⬇️