feat: add simple for loop and example

examples/04_loops.styve

src/frontend/Constants.java

src/frontend/ast/ASTPrettyPrinter.java

src/frontend/ast/BreakStmt.java

src/frontend/ast/ContinueStmt.java

src/frontend/ast/ForStmt.java

src/frontend/ast/NodeType.java

src/frontend/lexer/CodeReconstructor.java

src/frontend/lexer/TokenType.java

src/frontend/parser/Parser.java

src/runtime/Interpreter.java

src/runtime/eval/Expressions.java

src/runtime/eval/Statements.java

src/runtime/values/RTBreakSignal.java

src/runtime/values/RTContinueSignal.java

src/runtime/values/rtValueType.java