feat: add while loops, break and continue statements

tests/fibonacci.src

@@ -0,0 +1,15 @@
+fn main() -> i32 {
+    let n = 10;
+    let a = 0;
+    let b = 1;
+    let i = 0;
+
+    while i < n {
+        let temp = a + b;
+        a = b;
+        b = temp;
+        i = i + 1;
+    }
+
+    return a;
+}