feat: better .env loading support

[typedarray]

Problem / use case

We currently only auto-load .env.local, but sometimes people like to use .env or .env.dev

Proposed solution

I like the approach Next.js uses (docs)

Environment variables are looked up in the following places, in order, stopping once the variable is found.

process.env
.env.$(NODE_ENV).local
.env.local (Not checked when NODE_ENV is test.)
.env.$(NODE_ENV)
.env