Add `rc.sort:...` option for convenience

Add shorthand syntax to sort current report.

We can do lots of filtering on whatever is the current report. But sorting doesn't seem to be as convenient.

I'm often writing things like `t rc.report.next.sort:,,...`, for on the fly sorting.

It would be nice if that was a little shorter, like `t rc.sort:,,...`.

I would say `sort:,,...`, but I just landed on the webpage https://taskwarrior.org/docs/deprecated.html, and noticed `limit:...` was deprecated in favor of `rc.limit:...`.

Or maybe this is an XY problem, and I'm not understanding that there's already a better solution, or that the above solution will complicate something.