COPYING file mentioned in header license is not present

https://github.com/rspatial/geosphere/blob/72d27173027454df8fd2cfa9c5b4af75279ccbc3/src/kissfft.h#L6

I believe you should also bundle the geographiclib file here, but also upstream appears to be missing it:

https://github.com/geographiclib/geographiclib/issues/29