Classic confinement for PortX

Apologies for the delay in reviewing this request.

FTP clients are a bit of an edge-case in regards to classic confinement as we have granted classic confinement for some in the past (Classic confinement for sFTP Client) whilst others have been able to work under strict confinement (Request for classic confinement: osync).

In this case, since PortX has the LocalShell feature, this then fits within the terminal emulators category defined in Process for reviewing classic confinement snaps plus the requirement to access arbitrary local files would seem to indicate this fits within the requirements for classic confinement.

As such, the requirements for classic confinement are understood. @advocacy could you please perform publisher vetting?