This uses the "Expand directories" feature introduces in Prettier 2.0 to automatically format all supported file types.
Also, I fixed some badly formatted files.
* Add babel-types package
`next dev` was failing with:
```
Error: Cannot find module 'babel-types'
```
* Upgrade to the latest bs-platform
Also add the `babel-types` package to stop the `next dev` command from complaining.
* Remove extraneous babel-plugin-bucklescript dependency.
Seems the dependency has been deprecated, and it doesn't seem to be required
anyways.