Improve detect openscad executable using `which`

[jeff-dh]

On my system openscad is installed in /home/xxx/.local/bin. Your detect executable function does not find it.

A call to which would provide a valid path to the executable:

>>> from shutil import which
>>> which("openscad")
'/home/xxx/.local/bin/openscad'
>>> 

[jreiberkyle]

Out of curiosity, what os/install path are you using?

[jeff-dh]

Linux, /home/xxx/.local/bin

[jreiberkyle]

closed by #18