Allow button config set via data attributes to be passed when initialising the component in JavaScript

[36degrees]

What

The button component currently uses a data-prevent-double-click data attribute to enable the 'prevent double click' functionality.

Update the button component so that the config can also be passed as an object when initialising the component in JavaScript.

As per #1708 (comment), any config passed via data attributes takes precedence over config passed when initialising a component.

Why

This aligns the general concept of 'component config' with the approach we're using for internationalisation.

Who needs to work on this

Developers

Who needs to review this

Developers

Done when

• The 'prevent double click' functionality can be provided when instantiating a Button object
• The 'prevent double click' functionality can be provided when instantiating a Button object via initAll
• If a data-prevent-double-click data attribute is present on the $module HTML element it overrides any config set via initialisation
• Tests to cover the above