Construct a forest_ipld::Ipld roughly matching JSON format. This code is a modified version
of serde_json::json macro, with extensions for being able to indicate links and bytes.
These two matterns can be matched by wrapping Cid link in Link(..) or the Vec<u8> in
Bytes().
Describes a series of steps across a tree or DAG of Ipld,
where each segment in the path is a map key or list index.
Path is used in describing progress in a traversal; and can
also be used as an instruction for traversing from one Ipld node to another.