feat: add conditional required, fix formatting in document.js, fix async calls for submit and revert.

[18alantom]

• Added conditional required, required can be a function that receives a subset of doc.
• The subset here consists only of fieldname and fieldvalues.
• Doc itself is not passed so as to prevent side effects.

Required can now be set like so.

fields: [
    {
      fieldname: 'paymentMethod',
      label: 'Payment Method',
      fieldtype: 'Select',
      options: ['', 'Cash', 'Cheque', 'Transfer'],
      required: 1
    },
    {
      fieldname: 'referenceId',
      label: 'Ref. / Cheque No.',
      fieldtype: 'Data',
      required: (doc) => doc.paymentMethod !== 'Cash'
    },
]