Feature request: cross-var

(There's a closed issue about this but it doesn't seem to have been closed responsively?)

cross-env is great but doesn't solve all the potential issues between BASH and PowerShell, among other things. Adding [cross-var](https://www.npmjs.com/package/cross-var) would solve all the *rest* of those issues (mostly involving quotes requirements for CLI args). Please consider adding a second method for it, alongside cross-env?

The issue names no repository files, tests, or entry points. Start by locating the existing cross-env integration and compare it with cross-var's handling of quoted CLI arguments; done means a second method supports the remaining Bash and PowerShell argument cases alongside cross-env.

Written by the indexing model from the issue text.