Is your feature request related to a problem? Please describe.
Currently, we accept arbitrary offsets, but they cannot be auto-adjusted to match your facing direction. We need new syntax and complicated math.

Describe the solution you'd like
I don't have a solution in mind, this is open to suggestions on how we could parse a "facing arbitrary vector".

Describe alternatives you've considered
The alternative is we do not add this feature, and users must manually change vectors to match their facing direction. It's not a great experience.

Additional context
Forked from #1363.

Note: this will be status:pending and not worked on until syntax is suggested. That is the big blocker on this.

Current proposal is to duplicate Mojang's syntax, ^: https://minecraft.gamepedia.com/Commands#Local_coordinates:_Caret_notation

Usage is //stack ^5,0,3. Cannot be partially applied, will always be applied entirely.