Add discord env variables to release job (#59)

## Summary
We updated the release process to automatically announce on Discord, but we forgot to pass those secrets as environment variables. As a result, the release process fails and I'm unable to release version `0.0.4`. This PR fixes that.

## How was it tested?
I'll test by trying to release again.

Version 0.0.3

Fast follow based on community feedback:
+ Improve the speed of the first call to devbox shell
+ Add console output explaining what's about to happen
+ Better error message when nix is not installed or in PATH
+ Error on "shell-inception". When calling devbox shell and
  you're already in a devbox shell.

[devbox] Add information to the README on how to join our Discord (je…

…tify-com#2607)

TSIA

Release devbox version 0.0.2

[devbox] Remove timestamp from dev releases (jetify-com#2565)

## Summary
Remove timestamp from dev releases, so that nightly releases can clobber the old files. Otherwise we end up with a single development release that has tons of binaries.

## How was it tested?
N/A

## Is this change backwards-compatible?
Yes