Next .env file

[vicb]

We have a @next/env shim to disable the loading of the .env files. This was needed to prevent accessing the filesystem.

We should inline the values at build time so that we can set them on process.env.

We will probably need a NEXTJS_ENV var that we could set to development in a .dev.vars to load the dev variables when running locally via wrangler dev. When deployed NEXTJS_ENV should load the prod vars if unset or whatever vars it points to when set.