Promise / async/await support

Hi,

Thanks for this library!

I use koa@2 that supports async/await syntax. My use case is:

const forms = require('forms')

let myForm = forms.create({
  username: fields.string({ required: true })
})

// POST request handler
app.use(async function(ctx) {
    let boundedForm = myForm.bind(ctx.request.body)
    let errors = await boundedForm.validate() // <-- I need syntax like this
    if (errors) {
      ctx.render('index', {
        form: boundedForm.toHTML()
      })
    } else {
      ctx.body = 'form is valid'
    }
})

What do you think about support of promises (promisification)?

---

Currently, I forced to use my wrapper around this library. It promisifies validate function:

const forms = require('forms')

let {create} = forms

forms.create = function (fields, options) {
  let form = create(fields, options)
  let {bind} = form

  form.bind = function (data) {
    let boundedForm = bind(data)
    // @see https://github.com/caolan/forms/blob/v1.3.0/lib/forms.js#L45
    let {validate} = boundedForm
    boundedForm.validate = function () {
      let deferred = new Deferred()
      validate(deferred.resolve)
      return deferred.promise
    }
    return boundedForm
  }

  return form
}

class Deferred {
  constructor() {
    this.promise = new Promise(this.onPromise.bind(this))
  }
  onPromise(resolve, reject) {
    this.resolve = resolve
    this.reject = reject
  }
  resolve() {}
  reject() {}
}

module.exports = forms

[caolan]

@voxpelli regarding the github org request: if @ljharb would like me to move the repository to an organisation, or simply add new collaborators here, I’m happy to do it. I’d rather not have the complexity of a new organisation for a small module myself, but I’ll follow @ljharb’s lead.

[ljharb]

If it’s reachable, it’s public ¯\_(ツ)_/¯ certainly a maintainer could choose to be capricious and break someone knowingly, but i certainly wouldn’t do that.