The PortableBlockItem interface provides a way to handle different
types of 'Block Items' within the Portable Text.
Every such block item is identified by the blockType property.
A block of text within the Portable Text document. This is the most common and popular block item
within the Portable Text instance. Most of the fields are based on the specification for Portable Text,
which can be seen here: https://www.portabletext.org/
