Float to string with fixed precision

In Javascript, I am able to do:

```javascript
const value = 0.8999999999
const roundedValueAsString = value.toFixed(2)

console.log(roundedValueAsString) // "0.90"
console.log(typeof roundedValueAsString) // "string"
```

There is similar [behaviour](https://stackoverflow.com/a/55582564) in Elixir