Do not use deprecated add-path command #71

As indicated in https://github.blog/changelog/2020-10-01-github-actions-deprecating-set-env-and-add-path-commands/ - the set-env and add-path workflow commands will be removed very soon as they can be exploited as shown here.

It appears that scan-action is currently using the add-path command although it is not really clear which subsequent action steps would even use the updated path. If the path was actually needed in subsequent commands, there is a new, file system based way of passing info between steps as described here.