Add support for savanna.alxafrica.com project pages.

[iSLAm4522]

Issue: The extension fails on https://savanna.alxafrica.com/projects/ with the error "This is not an ALX project page! 🐞" because it only checks for intranet.alxswe.com.

Proposed Fix: Update the handleAction function to include savanna.alxafrica.com. Suggested code:

if (
  !tab.url.startsWith("https://intranet.alxswe.com/projects/") &&
  !tab.url.startsWith("https://savanna.alxafrica.com/projects/")
) {
  showPopup("This is not an ALX project page! 🐞");
  return;
}