Add proper formatting of JSON in Dart and C#

[webholik]

Fixes #459
C#:

using RestSharp;
namespace HelloWorldApplication {
  class HelloWorld {
    static void Main(string[] args) {
      var client = new RestClient("http://example.com");
      client.Timeout = -1;
      var request = new RestRequest(Method.GET);
      request.AddHeader("Content-Type", "application/json");
      var body = @"{" + "\n" +
      @"    ""hello"": ""world""," + "\n" +
      @"    ""this"": true," + "\n" +
      @"    ""call"": [1,2,3,null]" + "\n" +
      @"}";
      request.AddParameter("application/json", body,  ParameterType.RequestBody);
      IRestResponse response = client.Execute(request);
      Console.WriteLine(response.Content);
    }
  }
}

Dart:

import 'dart:convert';
import 'package:http/http.dart' as http;

void main() async {
  var headers = {
    'Content-Type': 'application/json'
  };
  var request = http.Request('GET', Uri.parse('http://example.com'));
  request.body = json.encode({
      "hello": "world",
      "this": true,
      "call": [
          1,
          2,
          3,
          null
      ]
  });
  request.headers.addAll(headers);
  
  http.StreamedResponse response = await request.send();
  
  if (response.statusCode == 200) {
    print(await response.stream.bytesToString());
  }
  else {
    print(response.reasonPhrase);
  }
  
}

[umeshp7]

The space will depend on the indentation right? @webholik

[webholik]

@umeshp7 The problem is that if the indentation is using tabs, then we have no way to handle that with JSON.stringify. So I decided to use constant indentation for all cases.