Add donors scraping CGI scripts

[Xpirix]

Fix for #426

Summary:

• Get the script stripe_donor_logger.cgi and its dependencies from the old repo
• Update and test them locally
• It should be set up with nginx on the server side and ensure that the webhook link on stripe points to it. Please find the proposed change for that at: https://github.com/qgis/QGIS-Sysadmin-Documentation/pull/66

The cgi script will:

• Be called whenever a donation has been made on stripe
• Receive the donation information
• Add the donor name to the file donors.json
• Pull from the origin repo, commit and push this change to the main branch

For this change, I kept the process of manual deployment for now.

[timlinux]

Let me chat with @andreasneumann a bit about this - I am not too mad about turning our static site back into a dynamic site. Maybe we can implement this on a GH action rather or on a server that is not exposed to the internet....