Support synthetic primitives

[skonves]

Context

Currently, all literal values are assumed to come from the source content; however, in come cases, a parser may need to synthesize a value that does not. When these values violate various rules, it can be confusing for developers. They are told there is a mistake in the source material, but they don't have agency to make any changes.

Change

• Add a optional synthetic: true property to the literal types

Consequences

• Parsers can opt into indicating non-source content
• Rules can opt into ignoring values in synthetic literals