I upgraded a typescript project to native es modules and imported
`InvalidOptionArgumentError` was undefined at runtime, tho typescript
defined it as an alias to InvalidArgumentError.

```
import { InvalidOptionArgumentError } from 'commander'
//       ^ No type error here, typescript thinks InvalidOptionArgumentError should exist

assert(InvalidOptionArgumentError != null); // But it doesn't, this will throw an error
```

A quick test showed that there was a difference between the commonjs and
ecmascript module. The issue wasn't limited to typescript.

```
const { InvalidOptionArgumentError } = require('commander')
assert(InvalidOptionArgumentError != null);
```

```
import { InvalidOptionArgumentError } from 'commander'
assert(InvalidOptionArgumentError != null); // This will throw an error
```

This commit fixes the issue by exporting InvalidOptionArgumentError from
the esm entry point. Alternatively we could remove
InvalidOptionArgumentError from typings, I'm happy as long as build and
runtime match.

Co-authored-by: John Gee <john@ruru.gen.nz>