Add VR asset item
add_vr_asset_item(my_html, into, id, src, ...)html in a vector of strings; output from 'create_html'.
character string; unique identifier of a line in the html. Element id is highly recommended.
character string; asset id for future referral.
character string; path to asset.
Extra parameter that goes into a tag, e.g. In <div type = "xxx">, 'type = "xxx"' goes to ... .