[Release] .env preparation description is missing in dev/release/README.md

[kou]

Describe the bug, including details regarding any error messages, version, and platform.

We need to prepare dev/release/.env to run dev/release/release_rc.sh. We should explain it in dev/release/README.md.

[jbonofre]

Yup, good point. Let me propose a PR about that if it works for you 😄

[kou]

Thanks!