Infobox builder merge

This `addClass` could be nested with the calls below which is more consistent with the style used elsewhere, i.e.
``` php
		cell
			:addClass( InfoboxBuilderView.vars.Theme .. '-infobox-line-right' )
			:tag( 'div' )
				:addClass( 'mw-collapsible mw-collapsed ' .. InfoboxBuilderView.vars.Theme .. '-infobox-toggle-content' )
				:wikitext( field.Value )
				:done()
```