Implement linked views in image viewers

[astrofrog]

This is an often requested feature, and I have an issue in the core to keep track of this: glue-viz/glue#623

[robintw]

That's great - thanks! This feature is literally my 'holy grail', and will really enable a lot of cool satellite imaging stuff in glue.

This may be a request too far, but I thought I'd mention it... Would there be any way within this linked views framework to support displaying the details of the pixel underneath the mouse cursor in every image viewer window? So, if I hover over a pixel in Viewer 1, I can also see the data value in the pixels in Viewer 2, Viewer 3 etc?