Fix Linux path

Author: mmicu

USAGE.md

@@ -8,7 +8,7 @@ docker build -t pfci:latest .
 docker run --rm pfci:latest make linter
 # Generate PDF
 docker run --rm -v %cd%\artifacts:/repo/artifacts pfci:latest make pdf    # Windows
-docker run --rm -v $(pwd)\artifacts:/repo/artifacts pfci:latest make pdf  # Linux
+docker run --rm -v $(pwd)/artifacts:/repo/artifacts pfci:latest make pdf  # Linux
 ```
 
 ## Without docker