Make release workflow more robust

[fvictorio]

When publishing 0.3.6, we had an issue where one of the builds wasn't published. The underlying reason was that the meaning of macos-latest as an OS value changed since the last release. This was fixed in #415, but we should make some deeper changes to prevent this from happening again.

At the very least, we should add a step that checks that all the crates/edr_napi/npm directories have a .node file, or fail otherwise. But there might be other things we can do instead or in addition to this.