Export env vars from config

[reitzig]

sketches fix for #36

I don't speak JS/TS and don't even have a running developer environment; these are just some doodles. Can you take over, @jdx ? 🙏

I notice that the action currently uses shims; seems to me we could use PATH from mise env instead? Then we'd probably have to split setEnvVars and run mise env after mise install? 🤔

[jdx]

It uses shims so it can use config files from sub-directories.

[reitzig]

@jdx , is this something that can be expanded into a proper fix for #36, or can we scrap it?

[GreyTeardrop]

Would be really great to have this.
I believe if we run mise --env after mise install, we should be able to also export tool-specific environment variables. For us, that would help with setting proper JAVA_HOME when installing Java via mise-action.