addition: Managing of parenthesis

Its a fucking mess, i was writting straight bullshit but it conceptually
should work, just need to refactor the shit out of it to make it way
more clean than it actually is and also later fix the fucking evaluator
like damn it sucks ASSS now (not that much really is nice but obviously
doesn't work, i like my code a lot :)

include/lexer.h

@@ -11,6 +11,7 @@ typedef enum {
     NODE_INTEGER,
     NODE_BINARY_OP,
     NODE_UNARY_OP,
+    NODE_PARENTHESIS,
 } ASTNodeType;
 
 // For classify operators
@@ -21,6 +22,8 @@ typedef enum {
     OP_DIV,
     OP_POW,
     OP_FACTORIAL,
+    OP_START_PAR,
+    OP_END_PAR,
 } Operator;
 
 typedef enum {
@@ -46,6 +49,10 @@ typedef struct ASTNode {
             struct ASTNode *val;
             Operator op;
         } unary;
+        struct {
+            struct ASTNode *val;
+            Operator op;
+        } parenthesis;
     } data;
 } ASTNode;