Feature/ast - #2

…r Literal, Variable, Identifier, Assignment, MemberAccess, Program, BinaryOperation, EchoStatement, and NoOp

…or various AST nodes

…ray representation

…ssions, ParserInterface definition, and unit tests covering various scenarios

…ST traverser integration, improve string handling in Lexer, and add new unit test for string resolution

…sing closing parenthesis

…ted in TODO list

… and adjust spacing in string concatenation and class definitions

… tests for consistency and clarity