Export issue with package

```
Failed to compile
./node_modules/@blockstack/stacks-utils/dist/index.mjs
Can't import the named export 'b58ToC32' from non EcmaScript module (only default export is available)
```

Occured with following code:

```js
import { validateStacksAddress } from '@blockstack/stacks-utils'
export const validateSTX = memoize(addr => validateStacksAddress(addr))
```