Add parameter mode enums to computer

IntComp/Computer.js

@@ -13,6 +13,11 @@ module.exports = class Computer {
             MULTIPLY: 2,
             HALT: 99,
         };
+        this.PARAMETER_MODES = {
+            POSITION_MODE: 0,
+            IMMEDIATE_MODE: 1,
+        }
+        this.paramMode = this.PARAMETER_MODES.POSITION_MODE;
     }
 
     /**