README: concise overview of he2mif/, he2st/ and the new sdk/ folder

sdk: README for the two example H&E slides

sdk: add NCBI920.tif (H&E slide)

sdk: add CRC11_HE_registered.ome.tif (H&E slide)

he2mif/: ship the ORION-CRC slice as one tar (2,536 loose files hit the download API rate limit)

Dataset card: document he2mif/ and he2st/, per-folder licenses

Add he2st/: the MuPaD-HE2ST example slides (NCBI917, NCBI920) moved from MuPaD-HE2ST-examples

Add he2mif/: ORION-CRC example slice for 5-HE2mIF (600 train / 120 val / 120 test tiles)

initial commit