Testing of output for the different plots

We can get some inspiration from squidpy for testing the output of the different plots that napari-sparrow generates:

"Ground truth" matplotlib output is stored as images in the tests folder.
A PlotTester class saves a matplotlib plotting context to an image file and then compares this image against the ground truth image.
Plot output images are compared using matplotlib's compare_images function.

saeyslab / napari-sparrow