Remove the CLI config file

👋 - I was looking at updating the docs for RN around the cli-config.js file, and in digging around in the RN source code, I noticed that we might not need to do that anymore.

Basically, we added the cli-config to ensure that [this code](https://github.com/facebook/react-native/blob/04aaa01991b2b6af9587f4edb6a897e05fc5e1f8/local-cli/dependencies/dependencies.js#L28-L33) could resolve to this dep.

But passing in
```
yarn start --transformer "node_modules/react-native-typescript-transformer/index.js" --sourceExts "ts"
```

should also work, and in an ideal case support in RN could be improved to handle

```
yarn start --transformer "react-native-typescript-transformer" --sourceExts "ts"
```

Meaning a bit less process, it's a trade-off, and not one I'm sure I want to recommend yet - but worth noting