I just installed and its complaining about no bun

Over the years I've never had any issues installing or using pm2 but now I can't even get it running.

```
[PM2][ERROR] Interpreter bun is NOT AVAILABLE in PATH. (type 'which bun' to double check.)
```

But I never used bun and at this time have no interest in using it.  Is this now a dependency?  If so, maybe some mention of it being a requirement in the docs would be merciful.