Add subContentId as attribute to interaction div

[skills-up]

Allows uniquely accessing the interaction via JS and CSS

[otacke]

If you add custom attributes to HTML elements, you should follow the data-* syntax for that purpose, please cmp. https://developer.mozilla.org/en-US/docs/Learn/HTML/Howto/Use_data_attributes

[skills-up]

I've actually followed already included aria-label convention

[otacke]

I am not sure if I understand what you are referring to. aria-label is an inherent attribute of HTML DOM elements. sub-content-id is not and should be using the data- prefix reserved for custom attributes.

[skills-up]

Added the prefix, as required.

[otacke]

I didn't say it was required, but that one should do it that was as it is recommended. I am not part of the H5P core team anyway, so feel free to ignore me :-D