Add calculator and fibonacci examples

examples/calculator.tralla

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+// calculator.tralla
+// This example demonstrates basic arithmetic operations and variable usage.
+
+let num1 = 10;
+let num2 = 5;
+
+let sum = num1 + num2;
+print("Sum:", sum); // Expected: Sum: 15
+
+let difference = num1 - num2;
+print("Difference:", difference); // Expected: Difference: 5
+
+let product = num1 * num2;
+print("Product:", product); // Expected: Product: 50
+
+let quotient = num1 / num2;
+print("Quotient:", quotient); // Expected: Quotient: 2
+
+let result = (num1 + num2) * (num1 - num2) / num2;
+print("Complex Calculation:", result); // Expected: Complex Calculation: 15

examples/fibonacci.tralla

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+// fibonacci.tralla
+// This example calculates the nth Fibonacci number using a loop and a function.
+
+func fibonacci(n) {
+    if n <= 0 {
+        return 0;
+    }
+    if n == 1 {
+        return 1;
+    }
+
+    let a = 0;
+    let b = 1;
+    let i = 2;
+
+    while i <= n {
+        let temp = b;
+        b = a + b;
+        a = temp;
+        i = i + 1;
+    }
+    return b;
+}
+
+let num = 10;
+let result = fibonacci(num);
+print("The", num, "th Fibonacci number is:", result); // Expected: The 10th Fibonacci number is: 55
+
+num = 0;
+result = fibonacci(num);
+print("The", num, "th Fibonacci number is:", result); // Expected: The 0th Fibonacci number is: 0
+
+num = 1;
+result = fibonacci(num);
+print("The", num, "th Fibonacci number is:", result); // Expected: The 1th Fibonacci number is: 1