[legacy-framework] Add vanilla-extract recipe

[JuanM04]

Added vanilla-extract recipe

[beerose]

I think there's a bug with wrapping the config with createVanillaExtractPlugin — looks like the session is undefined, and there are multiple errors when accessing fields of the session context, e.g.: Cannot read property '$create' of undefined.

Here's also a related issue: blitz-js/legacy-framework#13, where wrapping the config causes the same problems.