Add `nrc_ta_image_comparison` function to trending tools #1122

Job	Run time
Coverage test in Python 3	11m 48s
Check for Sphinx doc build errors	1m 55s
Try Astropy development version	11m 15s
Try latest versions of all dependencies	10m 44s
Try minimum supported versions	10m 49s
Try released POPPY and PySIAF	10m 33s
	57m 4s

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