Sort command can result in invalid JSON/JS

Sorting doesn't seem to take the ending commas into account when sorting. This is problematic if you have something like this
```js
export default {
  "c": "c",
  "b": "b",
  "a": "a"
}
```
This will result in 
```js
export default {
  "a": "a"
  "b": "b",
  "c": "c",
}
```
Which is now invalid 😢.