feat(fetch-button): disable continue button conditionally on a loading value

[tahmidrahman-dsi]

Example for countryconfig implementation:

{
  id: 'sectionId',
  canContinue: '!$form.fetch.loading',
  fields: [
    //...section fields
    ],
}

[rikukissa]

Much better :)

[solomcfly]

Thanks @tahmidrahman-dsi