Get URL and Private Mode in Firefox Quantum (and previous version) in Windows
return value: A string with full URL: Examples: https:www.freelancer.com or http:www.freelancer.com
or empty is not available or some error code in case of error.
Note 1: This function could optionally receive the process that belongs to Firefox (or the function could get automatically)
Note 2: Only the URL of the active tab must be returned.
Note 3: If Private Mode is active. return '[login to view URL]'