Issue when lexing "true" & "false"

[Gipson62]

Description:

Literal::Bool(bool) is never constructed because "true" & "false" are considered as identifier and/or keyword, but not as a literal value like they should.

Steps to Reproduce:

Create a lexer using the `atlas-core` library.
Input the strings "true" and "false".
Observe that they are not recognized as `Literal::Bool(bool)`.

Expected Behavior:

"true" and "false" should be recognized and constructed as Literal::Bool(bool).

Actual Behavior:

"true" and "false" are considered as identifiers and/or keywords, and not as literal values.