Add `nvm rm` as an alias for `nvm uninstall`

Here's an excerpt from my bash history:

```bash
nvm i v20.10
nvm rm v20.9.0
nvm uninstall v20.9.0
```

`npm rm` is a synonym for `npm uninstall`, so naturally I try the same thing for `nvm`. Every single time, it barfs out a help string and I have to re-run the command with the full name. It would be more convenient if that alias existed.