[Request] Implement check for GCP distribution

[mradamcox]

Describe the feature or enhancement you're looking for
The automated georeferencing process developed by UT Austin (https://repositories.lib.utexas.edu/items/3f080054-8ff0-4e4c-8ef7-ea93b0fc36e0) implemented a novel approach to ensuring that GCPs are well-distributed across a given map. They use a convex hull operation on all points and then compare the area of the polygon against the full area of the image (see p18).

It would be great to implement something like this as a visual check during georeferencing, and, perhaps more importantly, calculate this ratio for all content that has already been georeferenced, such that we can easily look back through the work and correct sheets from the past that need help.

Additional context
It may be wise to use a cut-off within the georeferencing interface, such until a ratio is above a certain number, the GCPs cannot be submitted, thereby preventing the submission of GCPs that are likely to produce a very distorted map.