Parameters
- block: TypedObject | PortableTextBlock<PortableTextMarkDefinition, PortableTextSpan | ArbitraryTypedObject, string, string>
Returns block is PortableTextListItemBlock<PortableTextMarkDefinition, PortableTextSpan, string, string>
True if valid Portable Text list item block, otherwise false
Strict check to determine if node is a correctly formatted portable list item block.