fix: extract pid from pid column that sometimes contain process name

[Damilope]

Problem

Find by port doesn't work on some MacOS devices because the pid column from netstat contained processname:pid whereas the code was expecting just pid, which returns a NaN when run through parseInt(...)

I think it's the cause of issue 84.

Proposed change

Try to extract pid from processname:pid using a RegExp capturing group matching decimals :d and if present, parse into an integer, otherwise, use the cell as is.

Also added a check to only resolve the promise if the parsed process is a number, and reject otherwise.