Change list

• Implements the .crs attribute on the GeoTIFF.
• For simple CRSes that are described by an EPSG code, we return CRS.from_epsg(code)
• For custom CRSes that are described by custom elements in the GeoKeyDirectory, we use a (mostly Claude-written) implementation to parse the custom elements and construct a PROJJSON file.
• Adds tests for CRS equality with rasterio
• Adds tests for custom CRS equality with rasterio using feat: Add NLCD example geotiff-test-data#16
• Adds tests using jsonschema that the PROJJSON created validates against the PROJJSON json schema.