According to the web site,
" How Arc Welder Works
Arc Welder reads each GCode in the source file, searching for three extrusion or retraction commands in a row. It adds adds these points to a special shape detection class that determines if the collected points can be represented by an arc command (G2/G3)."
It’s looking for extrusion or retraction, so simply appending an Exx to the end of every G01 line would fool arcwelder into doing its thing, I think.
That should be easy with Notepad ++, at least for testing purposes.