Add support for `nextjs` Edge runtime

[BowlingX]

This is just a rough draft.

I think a better approach would be to use the export map to import different implementation. e.g.

import { parseEnv } from "znv/node";
import { parseEnv } from "znv/next-edge";

The default could just point to the node implementation (to make it backwards compatible). The easiest would possibly to make parseEnv a factory that allows to pass the reportErrors function.