Add if else if chains

Signed-off-by: Marcel Müller <neikos@neikos.email>

src/eval/mod.rs

@@ -67,6 +67,16 @@ pub fn execute(
                     }
                 }
             }
+            Instruction::Jump { jump } => {
+                let (new_ip, overflow) = ip.overflowing_add_signed(*jump);
+
+                if overflow {
+                    return Err(EvaluationError::InstructionPointerOverflow);
+                } else {
+                    ip = new_ip;
+                    continue;
+                }
+            }
         }
 
         ip += 1;