windows: Also search for file without added extension (#57)
windows: Also search for file without added extension (#57)

Previously if the extension of the file to be searched for was not in the
list of executable extensions (env var `PATHEXT`), the original file name
would not be searched.
E.g. `script.py` would result in `script.py.EXE`, `script.py.COM`, and so on
to be searched.

This change prepends the original file to the search list if it already has
a file extension so that the unmodified filename will be searched aswell.
fangyuanziti/which-rs