Enhance frame limit detection

[lcolladotor]

Currently https://research.libd.org/spatialLIBD/reference/frame_limits.html is limited to dimensions in Visium capture areas. We know that Visium HD will likely be larger. Also, the current function is slow and we should improve the speed in which frame limits are detected. Furthermore, the current functions are not compatible with stitched images (see #53).