Add jsformdata

[juancarlospaco]

• Wrapper for FormData object for JavaScript backend. A "key":"value" for the web browser.
• runnableExamples.
• https://developer.mozilla.org/en-US/docs/Web/API/FormData/append
• https://developer.mozilla.org/en-US/docs/Web/API/FormData/delete
• https://developer.mozilla.org/en-US/docs/Web/API/FormData/get
• https://developer.mozilla.org/en-US/docs/Web/API/FormData/getAll
• https://developer.mozilla.org/en-US/docs/Web/API/FormData/has
• https://developer.mozilla.org/en-US/docs/Web/API/FormData/set

import jsformdata

let data = newFormData()
data.set("key", "value".cstring)
data.append("key2", "value2".cstring)
data.delete("key2")
discard data.has("key")
discard data.get("key")

/* Generated by the Nim Compiler v1.0.99 */
/*   (c) 2019 Andreas Rumpf */
var framePtr = null;
var excHandler = 0;
var lastJSError = null;
if (typeof Int8Array === 'undefined') Int8Array = Array;
if (typeof Int16Array === 'undefined') Int16Array = Array;
if (typeof Int32Array === 'undefined') Int32Array = Array;
if (typeof Uint8Array === 'undefined') Uint8Array = Array;
if (typeof Uint16Array === 'undefined') Uint16Array = Array;
if (typeof Uint32Array === 'undefined') Uint32Array = Array;
if (typeof Float32Array === 'undefined') Float32Array = Array;
if (typeof Float64Array === 'undefined') Float64Array = Array;
var nim_program_result = 0;
var global_raise_hook_58618 = [null];
var local_raise_hook_58623 = [null];
var out_of_mem_hook_58626 = [null];
  if (!Math.trunc) {
    Math.trunc = function(v) {
      v = +v;
      if (!isFinite(v)) return v;

      return (v - v % 1)   ||   (v < 0 ? -0 : v === 0 ? v : 0);
    };
  }

var data_83014 = (new FormData());
data_83014.set("key", "value", "");
data_83014.append("key2", "value2", "");
data_83014.delete("key2");
data_83014.has("key");
data_83014.get("key");

[Araq]

This should be a Nimble package IMO.