started work on lexer

tests/variables.pla

@@ -6,8 +6,10 @@ myBoolean: Bool = true
 myString: String = "Hello!\n"
 myList: List = [1, "hi", true, [1, 2, 3], 0.789]
 
-write(String(myInt))
-write(String(myDecimal))
-write(String(myBoolean))
-write(myString)
-write(String(myList))
+MY_CONSTANT: Const(String) = "foo bar"
+
+print(String(myInt))
+print(String(myDecimal))
+print(String(myBoolean))
+print(myString)
+print(String(myList))