feat: Display aur pkgbuild diff when user upgrades aur package

ame should show a diff between pkbuilds for an aur upgrade (if the pkgbuild changes) that way its easier to see what the new pkgbuild does instead of having to review and compare everything manually

paru has this feature too, but i couldn't find where exactly in the code the pkgbuilds are checked. It probably should also be possible to disable this in the config