Add javascript FITS viewer functionality

[astrofoley]

We currently have only static images for postage stamps, etc. The automatic choices for things like dynamic range can often make it hard to see the desired features for a particular image.

Describe the solution you'd like

There is a javascript FITS viewer https://www.clearskyinstitute.com/fits/ that seems to handle this well. For instance, here are some examples:
https://lasair-iris.roe.ac.uk/fitsview/1961215622115015012_cutoutDifference/
https://lasair-iris.roe.ac.uk/fitsview/1961215622115015012_cutoutScience/

This is the solution LASAIR uses. They have links for specific images, which is probably smart if this is resource intensive. See their page: https://lasair-iris.roe.ac.uk/object/ZTF22aakcoin/ with links under the postage stamp ("This image is the most recent. Click on these links to inspect the science, ref, and diff images in detail.")

Describe alternatives you've considered

I haven't thought about other ways to solve this or looked for alternative codes that provide the same functionality.