[Feature] Char Parsing

[gluax]

🚀 Feature

The goal is to add char as a Token and for it to be parsable to AST nodes.
Depends on #939.

Motivation

This helps the implementation goal of #929.

Implementation

Tokenizer Side

• A new Char Token Enum should be created leo/parser/src/tokenizer/token.rs. This should go under the commented Types section.
• A new CharLit Token Enum should be created leo/parser/src/tokenizer/token.rs. This should go under the commented Types section.

Parser Side

• In parse_primary_expression should match on Token::CharLit and then parse the character to a AST Node ValueExpression leo/parser/src/parser/expression.rs.

Tests

• Parser Tests:
  • Escaped Characters.
  • Hex Characters(although I suppose these could be grouped with the prior).
  • Valid Regular Characters.
  • Invalid Character Syntax.