1Password support

Add support to have env vars come from onepassword vaults. Digging through some docs, we probably want to make the UX something like `epicenv set KEY --1password/-1 vault/item/field`. They have an official go sdk to load these: https://developer.1password.com/docs/sdks/load-secrets If seeking to monetize this with enterprises, maybe make this integration (and subsequent integrations) part of an enterprise license, meaning this would have to be dual licensed (keeping MIT for everything local + github keys). Would still be source-available, but must be activated (require internet connection, which is fine bc ent features will likely be integrations with internet connected services)