Update URLs in README.md
archboot.org doesn't resolve now, and the .com one is now using CDN.
Due to an influx of spam, we have had to temporarily disable account registrations. Please write an email to accountsupport@archlinux.org, with your desired username, if you want to get access. Sorry for the inconvenience.
archboot.org doesn't resolve now, and the .com one is now using CDN.