feat: 添加break和continue语句的支持，更新解析器、解释器和词法分析器以处理相关语法

examples/break_test.ast

@@ -0,0 +1,27 @@
+// test break
+let i = 0
+while (i < 10) {
+    if (i == 5) { break }
+    i = i + 1
+}
+print("break (expect 5):", i)
+
+// test continue
+let sum = 0
+let j = 0
+while (j < 10) {
+    j = j + 1
+    if (j == 5) { continue }
+    sum = sum + j
+}
+print("continue (expect 50):", sum)
+
+// test for + break
+let found = -1
+for (let k = 0; k < 100; k = k + 1) {
+    if (k * k > 50) {
+        found = k
+        break
+    }
+}
+print("for break (expect 8):", found)