Consider fork Stirling-PDF

[webysther]

Raasons:

• They started to become seriously commercial
• It's a APP which can be inside LibrePDF organization
• It's easy to remove the commercial features in this initial stage:
  • [Feature Request]: Option to disable "Upgrade to Pro" Stirling-Tools/Stirling-PDF#2974
  • [Feature Request]: Disable Survey Stirling-Tools/Stirling-PDF#1573
  • Tracking Pixel Sends Data Even When Users Opt Out Stirling-Tools/Stirling-PDF#3283

I will initially keep upstream and removing all commercial with a new build and a S6 docker image, if the project is interested to host the fork, let me know.