Accept array of maps as client.post body parameter

Hi guys!

I have post request with a body that look like this:

```
[
{
"text": "Some String",
},
{
"text": "Another String",
}
]
```

For reference:
Future post(url, {Map headers, body, Encoding encoding});

Now I can pass the body as String, but I would prefer it as List>. Right now the body parameter only accepts String, List or a Map.

Would that be possible?

Greetings,
Kevin