✨ [FEATURE]: Add labels default options

[thinkjrs]

Is your feature request related to a problem? Please describe.
It would be nice to be able to customize default label options, i.e. customize the headings and description on the inputs.

Describe the solution you'd like
Add labels key to the options config object, e.g.

<PromoButton
  labels={{
    adTitle: 'My default ad title',
    adTitleDescription: 'My short description',
  }} 
/>