Update README.rst

[jniggemann]

adds retirement warning

[jdchristensen]

I think it should mention borgbackup and give a link.

[jniggemann]

I think it should mention borgbackup and give a link.

I think we should not guide people to a specific solution, but either

• let them figure out what's available and suitable for their needs OR
• mention multiple different solutions available (borg, restic, dar, rdiff-backup,...)

[jdchristensen]

Borg is special since it's a fork of attic, and I think that fact should be mentioned. I don't think it makes sense to try to enumerate other options, since there are so many. "Borgbackup (link) was forked from attic in 2015. There are many other options as well."

OTOH, I doubt this matters much, since there have been no commits since 2015, so it's pretty clear that it's not active.