geiser-capf--company-location should return a buffer+pos pair or a file+line pair

Hello Jao!

geiser-capf--company-location should return a pair, either a buffer plus position or a file name plus line number, or nil if no location has been found, such that this functionality works properly with Company or Corfu.

See the relevant Company documentation:

`location': The second argument is a completion candidate.
Return a cons of buffer and buffer location, or of file and
line number where the completion candidate was defined.

See also the relevant Company source.

Right now the function geiser-capf--company-location seems to attempt jumping to the location directly.

Thanks!